R1:4d68c0ae044c

Make Herald test workflow modular and more clear

Summary:
Fixes T9719. Currently, the Herald "Test Console" has a big `instanceof` thing, so new adapters (like a Calendar adapter, or third-party adapters) aren't available automatically. Instead, do a standard modular thing: load the available adapters, ask which ones can test the object the user selected, then let the user pick which one they want to move forward with.

Additionally, it isn't very clear that you can't test "commit hook" rules because they…