Add baseline tests for deletion and queue processing

Problem/Motivation

Revision Delete Tools currently doesn’t have any automated test coverage. We should add some baseline tests to make sure the core functionality works as expected.

• Validating revision deletion on different entity types
• Testing how multilingual revisions are handled.
• Checking that queue batch processing runs smoothly.

I've added some similar tests in Revision Manager that we can probably reuse: https://git.drupalcode.org/project/revision_manager/-/tree/1.0.x/tests/s...