* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

This is an attempt to reland #18488 with less breakage on macOS.

This reverts commit 77508722.

Rather than complain about these in a code review I figured I'd just fix them. :-)

...for the port arguments

This ensures that accidental usages of dart:io's
file API don't creep in over time.

* 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

* convert flutter commands to use ToolExit for non-zero exit code
* add convenience method throwToolExit
* print ToolExit message iff not null

* cleanup obtaining user home directory path
* refactor doctor and detect IntelliJ on Mac
* fix detect Flutter plugin for IntelliJ

* rename service_protocol.dart to protocol_discovery.dart

* add a wrapper around the obs. protocol

* use json-rpc in run

* consolidate obs. code; implement flutter run --benchmark

* review comments

* rework flutter run

* fix npe with --debug-port

* connect to obs and exit when that conneciton closes

* update todos

Add a command that can capture a Skia picture of a Flutter frame and send it to a file or skiaserve debugger (#3165)

remove device type specific checks