The end goal here is to be able to use |mach try fuzzy <path>| with tests that
belong to a subsuite. To do this, we need a unique 'task_regex' value for each
subsuite so that we can map a test path back to a set of tasks.
This removes the TEST_FLAVORS dict (which was mostly just a redefinition of the
data in TEST_SUITES), and instead provides two new private mappings:
<flavor> -> suite definition
(<flavor>, <subsuite>) -> suite definition
To retrieve a suite definition given a flavor/subsuite, consumers can now call
get_suite_definition.
MozReview-Commit-ID: 2pe1v1IHUVy
86db9106de