This reverts commit 8e231796.

* Unit test for build.dart::GenSnapshot

* Fix analysis errors

* Switch to testLogger

This reverts commit 96482eeb.

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 

When the plugin list changes, iOS pods are invalidated, but that was
never wired up for macOS.

Should fix #39327

Moves the generated config into that directory. Matches the structure of
the other desktop projects.

Also fixes #40265

- 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.

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

Fixes #40238