With this change, mach test can now resolve filename arguments to tests
and can dispatch to the appropriate mach commands.
If the arguments contain tests belonging to multiple test
suites/flavors, each relevant test in invoked.
`mach test` now dispatches through `mach mochitest --flavor` where
supported. As part of testing this patch, it was discovered that `mach
test` may have been broken for quite some time, as it was still
referring to "test_file" arguments instead of "test_paths." This has
been corrected.
The future of running tests is this command. It is a unified command for
running tests. Currently, it only supports running test suites from
their full test suite name or TBPL abbreviation. Support will be added
in the future for running individual tests or mixing and matching tests
of different flavors.
