Slight cleanup of file locations in flutter_tools
to make it easier to see which files are responsible
for data reporting.

Move tools tests into a general.shard directory in preparation to changing how we shard tools tests (#36108)

Reland: Ensure that flutter run/drive/test/update_packages only downloads required artifacts  (#30254)

Revert "Ensure that flutter run/drive/test/update_packages only downloads required artifacts (#30075)" (#30232)

This pattern is problematic when Flutter is ported to build systems
that require each executable end-point to be self-contained (e.g.
Bazel).