[a11y] Make sure RenderFractionalTranslation updates its semantics after the translation field is set (#48985)

* 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

See #41880 for history.

This reverts commit 1781d5c9.

...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.

This reverts commit bd52a78c.

This reverts commit 71e9bd6f.

Apparently, this accounts for 13% of our crashes in Beta.

* enable lint unnecessary_new

* fix tests

* fix tests

* fix tests

All temporary directory start with `flutter_` and have their random component separated from the name by a period, as in `flutter_test_bundle.YFYQMY`.

I've tried to find some of the places where we didn't cleanly delete temporary directories, too. This greatly reduces, though it does not entirely eliminate, the directories we leave behind when running tests, especially `flutter_tools` tests.

While I was at it I standardized on `tempDir` as the variable name for temporary directories, since it was the most common, removing occurrences of `temp` and `tmp`, among others.

Also I factored out some common code that used to catch exceptions that happen on Windows, and made more places use that pattern.

* Upgrade everything except matcher.
* Roll matcher (and test)
* Adjust tests that depend on flutter:test directly to depend on a shim
* Require use of package:test shim and remove other references to package:test

It was causing problems rolling Flutter into Fuchsia

* re-enable lint unnecessary_const

* remove trailling whitespaces

* remove unnecessary const (after merge)

This reverts commit cc1cf13e.

The new matcher package deprecates isInstanceOf which seems eggregious.

In getFlutterRoot(), scripts loaded via data: URIs are URI encoded.
getFlutterRoot() scans the contents of the data for the file:// URI path
of the Flutter SDK, which itself is URI-encoded. The end result is that
if the SDK path contains a space, the embedded file:// URI will contain
a %20. When this is encoded in a data: URI, the contents are
URI-encoded, resulting in %2520, since the % is encoded to %25.

This patch decodes the data: URI before extracting the SDK file:// URI.