refactor: API Integration Tests workflow (#2324)

- Simplify the API integration tests by removing steps not needed (Node,
k8s, building docker, etc).
- Testing the UI, linting, formatting, etc should be done in a separate
workflow file
- Simplify Rust cache workflow.
  - By default it caches /target
- Removed Dockerfile and k8s deployment from CI.
  - You can just run `OpenObserve` in the background
- Replace `ubicloud-standard-16` with `ubuntu-latest` which is *FREE*.
  - Using 16 cores, 64GB of ram is an overkill for running tests.
- Don't run the CI if changes to `.md` files are detected.

Notes:
- Before caching building `OpenObserve` takes around 5-7 mins, after
cache it goes down to 1-2 mins.

tests/api-testing/.python-version

@@ -1 +1 @@
-3.11.6
+3.11.7