Part of https://github.com/flutter/flutter/issues/147883.
Excluding Fuchsia and the Web SDK, the remaining scripts are:
```sh
$ ./tools/find_pubspecs_to_workspacify.sh
/Users/matanl/Developer/engine/src/flutter/impeller/tessellator/dart/pubspec.yaml
/Users/matanl/Developer/engine/src/flutter/sky/packages/sky_engine/pubspec.yaml
/Users/matanl/Developer/engine/src/flutter/shell/vmservice/pubspec.yaml
/Users/matanl/Developer/engine/src/flutter/lib/snapshot/pubspec.yaml
/Users/matanl/Developer/engine/src/flutter/lib/gpu/pubspec.yaml
/Users/matanl/Developer/engine/src/flutter/lib/web_ui/pubspec.yaml
/Users/matanl/Developer/engine/src/flutter/flutter_frontend_server/pubspec.yaml
```
These could be the trickiest, so I'm doing them separately.
The new `BUILD.gn` files in the Engine tree can't go under
`build/secondary` because Skia still has its own, and they'd be selected
first. So, this PR puts the new `BUILD.gn` files under `flutter/skia`.
fixes https://github.com/flutter/flutter/issues/130682
This patch makes all zip files created via the zip_bundle rule have an embedded LICENSE that points to a permalink to the LICENSE for that SDK commit hash. Previously we only did this for a few tools, but it was pointed out that some of the zip files we generate that are meant for consumption in the tool are otherwise missing a stand-alone license file (the tool downloads the full license file separately from the individual zips, as it would be costly to include it with each and every one).
