refactor executing tests to centralize actually invoking tests

Before this commit, tests were invoked in multiple places, especially
due to `-Z panic-abort-tests`, and adding a new test kind meant having
to chase down and update all these places.

This commit creates a new Runnable enum, and its children RunnableTest
and RunnableBench. The rest of the harness will now pass around the enum
rather than constructing and passing around boxed functions. The enum
has two children enums because invoking tests and invoking benchmarks
requires different parameters.

0 files changed, 0 insertions, 0 deletions