Currently, most options are 1:1 from the Gradle plugin extension to MetroOptions. However, there is some logic that is only present in the gradle plugin: interop. If anvil/KI/dagger interop is enabled, the gradle plugin wires the appropriate custom annotations there. Let's move this logic to MetroOptions itself (and introduce new options for interop to signal this).

This would afford two benefits:

• Dedupe the custom annotations logic. Currently compiler tests partially reimplement these replacements for interop tests since they don't use the gradle plugin.
• It would make this more approachable for non-gradle build systems like Bazel and Amper.