interfaces: add a Protocol class for `scmutil.status` I initially tried moving this to the `interfaces` package, both to have more cleanly defined interfaces (interfaces shouldn't have to reach into implementation files for their type info), and because importing `mercurial.ui` either directly or indirectly into `interfaces.repository` causes a situation where pytype stops inferring the type for `revlogutils.constants` that are imported by `revlog`. (Likely this is caused by a cycle. The `dirstate` interface already imports `scmutil`, which in turn imports `ui`, so the `repository` interface module importing the `dirstate` interface module as part of converting those classes to Protocol classes will trigger the issue.) I gave up on moving the class because `scmutil.status` depends on `stringutil`, which has a surprisingly long tail of dependencies. In any event, a standalone Protocol class might help with the Rust code.