* Add CocoaPods sudo installation note

* Refer to instructions

This message is displayed if we do not find a pubspec.yaml

99% of the time this additional advice is going to have nothing to do with the actual error. Just remove it because it will cause more confusion than it could clear up

Updates the tooling to use the GTK embedding, rather than the GLFW embedding:
- Adds new requirements to `doctor`
- Updates the app and plugin templates to make GTK-based runners and plugins
- Stops downloading and installing the GLFW artifacts

Final part of #54860, other than cleanup.

Current versions of the Windows desktop build files don't require a specific Windows 10 SDK version, but doctor still checks for one since vswhere doesn't allow for flexible queries. This has been a common source of issues for people setting up on Windows for the first time, because the current VS installer by default only includes a newer version of the SDK than what doctor is looking for.

This removes the vswhere SDK check, and instead uses a manual check for SDKs. Since this uses undocumented (although fairly widely used, so relatively unlikely to change) registry information, the check is non-fatal, so that builds can progress even if the SDK isn't found by doctor; in practice, it's very unlikely that someone would install the C++ Windows development workload but remove the selected-by-default SDK from the install.

Now that all requirements are default, the instructions when missing VS have been simplified so that they no longer list individual components, and instead just say to include default items.

Fixes #50487

Updates the Linux templates to use CMake+ninja, rather than Make, and updates the tooling to generate CMake support files rather than Make support files, and to drive the build using cmake and ninja.

Also updates doctor to check for cmake and ninja in place of make.

Note: While we could use CMake+Make rather than CMake+ninja, in testing ninja handled the tool_backend.sh call much better, calling it only once rather than once per dependent target. While it does add another dependency that people are less likely to already have, it's widely available in package managers, as well as being available as a direct download. Longer term, we could potentially switch from ninja to Make if it's an issue.

Fixes #52751

* 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

This updates the flutter tool cache to download binary files for ideviceinstaller, ios-deploy, libimobiledevice, and dynamically linked dependencies from Flutter's GCP bucket.

This reverts commit 14d489ad.

This updates the flutter tool to cache binary files for ideviceinstaller, ios-deploy, libimobiledevice, and dynamically linked dependencies from Flutter's GCP bucket.

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.