Updates VisualStudio and VisualStudioValidator to use constructors instead of global injection. Updates VisualStudio test cases to prefer FakeProcessManager
Updates build_windows test to work without injected VisualStudio

* 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

* implicit-casts:false on flutter_tools

* use castStringKeyedMap

* address review comments

* address review comments

* fix issues after rebase

...because otherwise, processes that think they're manipulating your
filesystem will be doing crazy things the test is ignoring, leading to
(at best) failures and (at worst) flakes or disk corruption.

Fixes a crash introduced on #40011 due to an incorrect type in the vswhere search

Fixes #40238

Move tools tests into a general.shard directory in preparation to changing how we shard tools tests (#36108)

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.