Moves the checks that projects have been configured for desktop to a lower level, where they will cover more codepaths (e.g., 'run'), and improves them to check for native build projects, rather than just directories, to catch cases where the directory exists (e.g., due to accidental creation of generated files).

Also adds links to the error messages pointing to instructions on adding desktop support to a project.

Fixes #47145

* Update project.pbxproj files to say Flutter rather than Chromium

Also, the templates now have an empty organization so that we don't cause people to give their apps a Flutter copyright.

* Update the copyright notice checker to require a standard notice on all files

* Update copyrights on Dart files. (This was a mechanical commit.)

* Fix weird license headers on Dart files that deviate from our conventions; relicense Shrine.

Some were already marked "The Flutter Authors", not clear why. Their
dates have been normalized. Some were missing the blank line after the
license. Some were randomly different in trivial ways for no apparent
reason (e.g. missing the trailing period).

* Clean up the copyrights in non-Dart files. (Manual edits.)

Also, make sure templates don't have copyrights.

* Fix some more ORGANIZATIONNAMEs

- Makes build_macos.dart handle the case where there is only one Xcode
  project in the macos/ directory, but it's not called Runner.xcodeproj
- Makes getInfo throw a tool exit when trying to get project info and it
  can't find a project, since that is a configuration error by the user
  rather than a tool bug.

Avoids unnecessarily breaking projects that have another .xcodeproj in
their macos/ directory, which worked until the addition of the getInfo
call.

Fix some places where Debug/Release was treated as a binary switch.

Makes similar changes to Windows and Linux to simplify adding profile
support to those platforms in the future. This means `--profile` builds
will fail on Linux and Windows for now, but that's fine since they
aren't actually supported, and unlike `--release` don't provide useful
functionality at the native code level.

Also fixes 'stopApp' always using Debug on macOS, to avoid showing an
error when running Profile (or Release).

Fixes #33203

Slight cleanup of file locations in flutter_tools
to make it easier to see which files are responsible
for data reporting.

- Adds desktop projects to ApplicationPackageStore
- Plumbs target overrides through the macOS build

Enables the CocoaPods-based plugin workflow for macOS. This allows a
macOS project to automatically fetch and add native plugin
implementations via CocoaPods for anything in pubspec.yaml, as is done
on iOS.

This is necesasry to integrate CocoaPods, since CocoaPods operates
primarily on the workspace rather than the project.

- Removes SYMROOT from the Generated.xcconfig. Having it causes current
  versions of Xcode to switch the project's build output to "Legacy",
  which causes anything not overridden to use a project-relative build
  directory instead of a shared directory in DerivedData, breaking
  anything with subprojects that it depends on.
  This means that `flutter run` and builds from Xcode will use
  completely different build directories, but that each should be
  internally consistent.
- Moves the FlutterMacOS.framework to $SRCROOT/Flutter. This is
  consistent with the approach we're moving to for all desktop
  platforms, and avoids issues finding it now that SYMROOT doesn't match
  for the two different build modes.

Fixes #32494