Allow running tests by line and column (#1604)

Fixes https://github.com/dart-lang/test/issues/1579

- Allows querying tests by line & col using test path query strings
- Matches if any frame in the test stack trace matches up (this allows for lots of flexibility in terms of testing styles and parameterized tests).
- If a stack trace formatter is set up for the remote platform, it will use it to format the `trace` sent back for groups/tests that are discovered (enabling browser/node support). 
12 files changed