Minimal tests (including some binding tests) and extended tests.

[qinsoon]

We should include some binding tests in the required mmtk-core. The tests are expected to finish in roughly half an hour or so (similar to our current mmtk-core 'pre code review' tests). If we include binding tests, the binding tests should cover some features in MMTk core that is only used by that binding, such as conservative stack scanning in Ruby, discontiguous VM space and transitively pinning in Julia.

We may need to allow a way to specify which binding branches to run in the PR description (currently we can only specify binding branches in PR comments). Otherwise the tests will always fail if a PR has API changes.

We should consider renaming our current tests to minimal tests, and extended tests. The name 'binding tests' is confusing, as it sounds like testing the bindings not mmtk-core.

[k-sareen]

Perhaps a better name would be integration tests?

EDIT: As in, "Julia Integration Test", "OpenJDK Integration Test", etc.