* remove locale "sd" (not supported by ICU/CLDR); unify localizations scripts CLI

* address comments

* misc .arb fixes; localizations validator

* regenerate localizations

* address comments

* do not treat plural variations as invalid keys

Also, add tests to verify that our coverage is actually being tested!

And add a test to verify we don't do this again.

We suspect maybe recent failures are caused by race conditions from
running flutter_tools tests in parallel.

Now that we can host packages on pub that depend on Flutter, we can host
flutter_markdown in its own git repository.

In particular, if stdout.supportsAnsiEscapes is false, don't output ANSI.

Also, output stdout/stderr of tests that are normally silenced, if they fail.

Also, update the output to be more convenient when debugging.

Also, expand some abbreviations.

We keep breaking --watch because we don't test it.

`all.dart` is no longer needed. Furthermore, it causes tests to
be skipped, or to silently fail to run anything.

Fixes #7941

This reverts commit fac9efba.

The timeout was fixed by 6795c4ab.

... and run some more tests on Windows.

Also, actually run the flutter_markdown tests.

* disables all `flutter test` and `flutter drive` tests on Windows as those two commands are not fully implemented on Windows yet
* fixes other failures on Windows