Matan Lurey 887fcf0563 Add and use a dart_test rule. (flutter/engine#55630) ...

Work towards https://github.com/flutter/flutter/issues/147013.

I think I still need applicable metadata about the output, and then make
sure `et test` understands everything:

```sh
% et test //flutter/tools/engine_tool/...
[2024-10-03 13:26:42.657137] ERROR: No test targets found
```

2024-10-03 14:41:25 -07:00

..

flutter

Add and use a dart_test rule. (flutter/engine#55630)

2024-10-03 14:41:25 -07:00