Remove flutter create --with-driver-test . Fixes #64095

Based on feedback from various desktop developers, and to be consistent between the defaults and the sample code, this PR switches the default for visual density in desktop themes to be compact instead of standard.

It also removes the same setting from the sample code generated by "flutter create" because it is no longer needed now that it is the default.

Adds a VisualDensity.adaptivePlatformDensity static function that returns different values for visual density based on the defaultTargetPlatform. Returns compact for desktop platforms, and a default visual density for other platforms.

This PR adds the linux and windows target platform enum values, along with automatically setting the defaultTargetPlatform to the appropriate value on those platforms.

Fixes #31366

This PR adds TargetPlatform.macOS to the TargetPlatform enum. This allows us to begin implementation of some adaptive UI based on which target platform is desired.

I haven't updated the tests here, that will come in a follow-up PR.

Adds macOS support for `flutter create`:
- Currently it is behind a hidden flag.
- Adds a TargetPlatform workaround to lib/main.dart in the standard app template when enabled.
- Supports `app` and `plugin`; `module` support doesn't yet exist for macOS in general.

This will eliminate the need to use FDE's examples as templates on macOS. The templates are based on the current state of FDE's examples, with templating support added (and with adoption of the new application delegate in the app, which hadn't been done yet in FDE, eliminating some boilerplate from the template).

Fixes #30703 

* update the docs for the module template

* update text

* Update template comments

Make template comments consistent with recent tools changes

* Update packages/flutter_tools/templates/app/lib/main.dart.tmpl
Co-Authored-By: mit-mit <mit-mit@users.noreply.github.com>

* Fix merge conflict

* Remove new keyword from default template app

This renames the "module" template to the "application" template, and makes "application" the default. The existing "app" template is now deprecated.

flutter create also now recognizes the type of project in an existing directory, and is able to recreate it without having the template type explicitly specified (although you can still do that). It does this now by first looking in the .metadata file for the new project_type field, and if it doesn't find that, then it looks at the directory structure. Also, the .metadata file is now overwritten even on an existing directory so that 1) the project_type can be added to legacy projects, and 2) the version of Flutter that updated the project last is updated.

I also cleaned up a bunch of things in create_test.dart, added many more tests, and added an example test to the test/ directory in the generated output of the application template.

Fixes #22530
Fixes #22344