Disable file watcher in VcsManagerTest suite

[4e6]

Pull Request Description

We can't really control the timing of file watcher events, which sometimes leads to failures of VCS tests. The PR disables the file watcher in the VcsManagerTest suite to make tests more stable.

Changelog:

• add: a Watcher and WatcherFactory interfaces
• add: a NoopWatcher test watcher
• update: disable the file watcher in the VcsManagerTest suite

Important Notes

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• The documentation has been updated, if necessary.
• All code follows the
  Scala,
  Java,
  and
  Rust
  style guides. In case you are using a language not listed above, follow the Rust style guide.
• All code has been tested:
  • Unit tests have been written where possible.

[hubertp]

Thanks!

[JaroslavTulach]

My wish is to cleanup the dependencies of our project. I believe there should be API (e.g. Watcher) visible to the rest of the code base, but the implementation should be in a different project.

My other wish: new files (Watcher, Watcher.Factory) would better be written in Java.

[JaroslavTulach]

This PR is a nice opportunity to separate API (e.g. Watcher) from the implementation and have them in different projects.

[JaroslavTulach]

The test shouldn't even see this class and definitely not io.methvin.watcher classes on the classpath!

[JaroslavTulach]

I'd make the WatcherFactory an inner class of Watcher if I was designing the API in Java.