[rllib] Cleanup BUILD.bazel and rllib.rayci.yml

[pseudo-rnd-thoughts]

Description

RLlib's rayci.yml file and the BUILD.bazel file are disconnected such that there are old tags in the BUILD not the rayci and vice-versa.
This PR attempts to clean up both files without modifying what tests are or aren't run currently

[gemini-code-assist]

Code Review

This pull request provides a much-needed cleanup of the test tags in rllib/BUILD.bazel and the CI configuration in .buildkite/rllib.rayci.yml. The changes significantly improve maintainability by simplifying the tagging scheme and making the CI steps more explicit and organized. The large-scale removal of unused and confusing tags in BUILD.bazel is a great improvement. My review identified one potential issue in the CI configuration that might unintentionally alter the set of tests being run, contrary to the PR's stated goal. A suggestion has been provided to address this. Overall, this is a valuable cleanup effort.

[kamil-kaczmarek]

@simonsays1980 Do you plan to use learning_tests_with_ray_data tag in BUILD.bazel? I don't see any tests with this tag added, yet we have it in rllib.rayci.yml. If you don't use it we will remove it to simplify.

I see that ray_data tag is in use, maybe we can just remove learning_tests_with_ray_data, as it looks like it's duplicate?

cc: @pseudo-rnd-thoughts

[kamil-kaczmarek]

Left few comments.

[simonsays1980]

learning_tests_with_ray_data

@kamil-kaczmarek (cc. @pseudo-rnd-thoughts ) I have never personally used this tag. So I think its safe to remove it.

[kamil-kaczmarek]

Notably this clean up removes following tags from BUILD.bazel:

• learning_tests_discrete
• learning_tests_continuous
• learning_tests_pytorch_use_all_core
• ray_data
• old_api_stack
• learning_tests_with_ray_data

[kamil-kaczmarek]

LGTM! Great work