Configure tags using annotation on test class

Similar to how heavy test annotation shows its own tag.
Something as simple as `TestTags("JS", "HMPP")` should do the trick.

The current "tags based on test class name" mechanism can co-exist with this, but migration might be a good idea regardless (so that test class renames don't cause issues)

Start by reading the existing heavy test annotation handling and the current mechanism that derives tags from test class names. Trace where those tags are configured, then add coverage showing that TestTags("JS", "HMPP") supplies tags while the existing mechanism can still coexist; done means the annotation works and the relevant tests pass.

Written by the indexing model from the issue text.