Increase Integration Tests coverage

[cdsap]

Most of the tests use a simple project where we configure the same scenario:

• Default configuration ( apply false for our plugin)
• Unique processor is applied in the test (Kapt/Apt/Ksp)
• Ksp is applied in the root build classpath

However, we didn't catch issues like #412. We need to increase the coverage for the different scenarios like:

• Multiple processors included in the same module
• Apply the plugin in non-Android projects
• Modules using kapt/ksp without the room-compiler
• Ksp is defined at the module level instead of the main build classpath.
• ...