This attempts to re-land #22656.

There are two changes from the original:

I turned off wrapping completely when not sending output to a terminal. Previously I had defaulted to wrapping at and arbitrary 100 chars in that case, just to keep long messages from being too long, but that turns out the be a bad idea because there are tests that are relying on the specific form of the output. It's also pretty arbitrary, and mostly people sending output to a non-terminal will want unwrapped text.

I found a better way to terminate ANSI color/bold sequences, so that they can be embedded within each other without needed quite as complex a dance with removing redundant sequences.

As part of these changes, I removed the Logger.supportsColor setter so that the one source of truth for color support is in AnsiTerminal.supportsColor.

*     Turn on line wrapping again in usage and status messages, adds ANSI color to doctor and analysis messages. (#22656)

    This turns on text wrapping for usage messages and status messages. When on a terminal, wraps to the width of the terminal. When writing to a non-terminal, wrap lines at a default column width (currently defined to be 100 chars). If --no-wrap is specified, then no wrapping occurs. If --wrap-column is specified, wraps to that column (if --wrap is on).

    Adds ANSI color to the doctor and analysis output on terminals. This is in this PR with the wrapping, since wrapping needs to know how to count visible characters in the presence of ANSI sequences. (This is just one more step towards re-implementing all of Curses for Flutter. :-)) Will not print ANSI sequences when sent to a non-terminal, or of --no-color is specified.

    Fixes ANSI color and bold sequences so that they can be combined (bold, colored text), and a small bug in indentation calculation for wrapping.

    Since wrapping is now turned on, also removed many redundant '\n's in the code.

Revert "Turn on line wrapping in usage and status messages, adds ANSI color to doctor and analysis messages. (#22656)" (#22759)

This reverts commit e4386321
because it breaks 160 benchmarks, and several devicelab tests,
due to changing the format of the output.

Turn on line wrapping in usage and status messages, adds ANSI color to doctor and analysis messages. (#22656)

This turns on text wrapping for usage messages and status messages. When on a terminal, wraps to the width of the terminal. When writing to a non-terminal, wrap lines at a default column width (currently defined to be 100 chars). If --no-wrap is specified, then no wrapping occurs. If --wrap-column is specified, wraps to that column (if --wrap is on).

Adds ANSI color to the doctor and analysis output on terminals. This is in this PR with the wrapping, since wrapping needs to know how to count visible characters in the presence of ANSI sequences. (This is just one more step towards re-implementing all of Curses for Flutter. :-)) Will not print ANSI sequences when sent to a non-terminal, or of --no-color is specified.

Fixes ANSI color and bold sequences so that they can be combined (bold, colored text), and a small bug in indentation calculation for wrapping.

Since wrapping is now turned on, also removed many redundant '\n's in the code.

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

Add iOS module template

This will enable integration of flutter-views into existing iOS project.

This reverts commit 8be198d8 that broke the build.

Add iOS module template

This will enable integration of flutter-views into existing iOS project.

Uses the `version` property from the `pubspec.yaml` file to set the corresponding fields in the `local.properties` file respectively in the `Generated.xcconfig` file.

The `--build-name` and `--build-number` options have changed. Now they trump the `version` property from the `pubspec.yaml` file.

If the `version` property is not set and the  `--build-name` and `--build-number` options are not provided, the build command will not change the `local.properties` / `Generated.xcconfig` file.

Package projects were erroneously being treated as apps

This reverts commit b3e4976c.

Adds a class `PubContext` with a fixed set of allowed values
Make it clear these values should not be changed casually

Fixed one inconsistency already: update_packages vs update_pkgs
Provide more information for verify calls
Eliminate `ctx_` prefix.

* Provide more information in PUB_ENVIRONMENT for `pub get/upgrade`

Should help diagnose and fix https://github.com/dart-lang/pub-dartlang-dart/issues/636

This makes command validation happen as part of `verifyThenRunCommand()`,
using a newly introduced protected method (`validateCommand()`) rather than
a `commandValidator` property (that subclasses were responsible for manually
invoking).

* Remove the workaround that pinned args to v0.13.6
This reverts most of the changes in commit 6331b6c8
* throw exception if exit code is not an integer
* rework command infrastructure to throw ToolExit when non-zero exitCode
* convert commands to return Future<Null>
* cleanup remaining commands to use throwToolExit for non-zero exit code
* remove isUnusual exception message
* add type annotations for updated args package

* convert pubGet to throw ToolExit on non-zero exit code
* convert commandValidator to throw ToolExit for non-zero exit code
* convert flutter commands to throw ToolExit for non-zero exit code
* use convenience method throwToolExit
* only show "if this problem persists" for unusual exceptions

This rewrites imports of various mojom.dart files from the Flutter
engine repo to instead import normal-looking dart files from the
(new) flutter_services package. This package handles exporting the
correct symbols from generated code wherever that may live.

Includes an engine roll to 3551e7a48e2e336777b15c7637af92fd7605b6c5
which contains the new flutter_services package.

* refactor _run to runCmd

* replace requiresProjectRoot getter with call to commandValidator

* replace requiresDevice getter with call to findTargetDevice

* trace command requires a debug connection, not a device

* inline androidOnly getter

* rename command methods to verifyTheRunCmd and runCmd

* move common verification into BuildSubCommand

* rename deviceForCommand to device

* rename methods to verifyThenRunCommand and runCommand

* implement flutter packages get/upgrade command
* alias flutter pub
* refactor findProjectRoot for use by multiple commands

fixes https://github.com/flutter/flutter/issues/4994