Disable CocoaPods input and output paths in Xcode build phase and adopt new Xcode build system (#34167)

Updates the Podfile template to use the CocoaPod disable_input_output_paths installation option which prevents the [CP] Embed Pods Frameworks build phase from outputting the Flutter.framework files.

Moves the logic for finding vcvars64.bat to a new VisualStudio class
that encapsulates finding, and providing information about, VisualStudio
installations. Adds a validator for it, and runs it for Windows
workflows in doctor.

Revert "Disable CocoaPods input and output paths in Xcode build phase and adopt new Xcode build system (#33852)" (#33882)

This reverts commit d053fe5c.

Disable CocoaPods input and output paths in Xcode build phase and adopt new Xcode build system (#33852)

Updates the Podfile template to use the CocoaPod disable_input_output_paths installation option which prevents the [CP] Embed Pods Frameworks build phase from outputting the Flutter.framework files.

Revert "Disable CocoaPods input and output paths in Xcode build phase and adopt new Xcode build system (#33684)"

This reverts commit ef792fc3.

Disable CocoaPods input and output paths in Xcode build phase and adopt new Xcode build system (#33684)

Updates the Podfile template to use the CocoaPod disable_input_output_paths installation option which prevents the [CP] Embed Pods Frameworks build phase from outputting the Flutter.framework files.

Revert "fix devicelab manfiest (#33698)"

This reverts commit 5a6a00dc.
This reverts commit 0d79f0fc.

Splits Xcode validation out of the iOS validator and into a stand-alone
validator, and groups the CocoaPods validator with that top-level
validator instead of the iOS validator. iOS now validates only the
iOS-specific tools (e.g., ideviceinstaller).

Reorganizes many of the associated clases so that those that are used by
both macOS and iOS live in macos/ rather than ios/. Moves some
validators to their own files as part of the restructuring.

This is the macOS portion of #31368

This reverts commit e5459942.

This is a cleanup PR.

Xcode 10 introduces a new build system which includes stricter checks on
duplicate build outputs.

When plugins are in use, there are two competing build actions that copy
Flutter.framework into the build application Frameworks directory:

  1. The Embed Frameworks build phase for the Runner project
  2. The [CP] Embed Pods Frameworks build phase that pod install creates
     in the project.

Item (1) is there to ensure the framework is copied into the built app
in the case where there are no plugins (and therefore no CocoaPods
integration in the Xcode project). Item (2) is there because Flutter's
podspec declares Flutter.framework as a vended_framework, and CocoaPods
automatically adds a copy step for each such vended_framework in the
transitive closure of CocoaPods dependencies.

As an immediate fix, we opt back into the build system used by Xcode 9
and earlier. Longer term, we need to update our templates and
flutter_tools to correctly handle this situation.

See: https://github.com/flutter/flutter/issues/20685

This caused issues for projects without an Xcode workspace. Almost all
Flutter projects in the wild will have a workspace, but this patch needs
to add a check to catch any that lack one.

This reverts commit 021f472e.

Xcode 10 introduces a new build system which includes stricter checks on
duplicate build outputs.

When plugins are in use, there are two competing build actions that copy
Flutter.framework into the build application Frameworks directory:

  1. The Embed Frameworks build phase for the Runner project
  2. The [CP] Embed Pods Frameworks build phase that pod install creates
     in the project.

Item (1) is there to ensure the framework is copied into the built app
in the case where there are no plugins (and therefore no CocoaPods
integration in the Xcode project). Item (2) is there because Flutter's
podspec declares Flutter.framework as a vended_framework, and CocoaPods
automatically adds a copy step for each such vended_framework in the
transitive closure of CocoaPods dependencies.

As an immediate fix, we opt back into the build system used by Xcode 9
and earlier. Longer term, we need to update our templates and
flutter_tools to correctly handle this situation.

See: https://github.com/flutter/flutter/issues/20685

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

* First step in Flutter Doctor refactor. Assigns categories to all validators.

* Revert "Roll engine e54bc4ea1832..a84b210b3d26 (6 commits) (#20453)"

This reverts commit 05c2880a.

* Split iOS and Android workflows into workflow and validator classes.

* Change ValidatorCategory to handle standalone validators that share a
category (e.g. IntelliJ).

Also make Android Studio and Android toolchain use separate categories.

At this stage, flutter doctor output matches what it was previously.
(The summary() method itself has not yet been changed )

* Change doctor summary code to support validator categories.

Output is still unchanged.

* Handle small formatting issues.

* Flip Flutter category's isGroup field to false until it's actually
needed.

* Revert auto-generated formatting changes to keep those lines from
muddying the pull.

* Small fixes pointed out by analyzer.

* Properly fix analyzer issues around const constructors.

* Small changes to address comments.

* Add tests to verify grouped validator behavior and validationtype
merging.

* Update doctor.dart

* Add comments for clarification.

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