Move selenium to root

[MarcialRosales]

Proposed Changes

Selenium tests are end-to-end tests. They currently verify two kind of functionality:

• management ui
• messaging protocols authenticating with multiple authentication backends

These tests have lived under deps/rabbitmq-management/selenium folder because they were initially meant for testing the management ui. But now, they are used to test other areas not only the management ui. Therefore, it is more appropriate that these tests live somewhere else, like in the root of this rabbitmq-server repository.

Additionally, the Gihub action that runs the management ui tests have been split into two GHA. One for push to main and another for PRs.

Note: This PR depends on #12165

Types of Changes

What types of changes does your code introduce to this project?
Put an x in the boxes that apply

• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)
• Build system and/or CI