docs: part 1 - fix warnings in documentation generation (#2861)

**Description**
This PR removes some of the warnings when uv builds the docs
- Errors appear when generating docs about .md files not appearing in
toctree. ~~Adding content to the `providers-gen.py ` file that adds `---
orphan: true ---` to to each file.~~. Added a toctree generator to the
`providers-gen.py` file, this gets rid of the errors in the builds.
- Deletes the `_openai_compat` files, extension of PR #2849
- Adds the `files` APIs section to the `providers` toctree on the index
page
- Manually adds the `--- orphan: true ---` to the advanced apis. Ill try
to find a way to modify the providers code gen so it automatically adds
it, but this fixes the errors.
- Adds the `testing.md` to the `contributing` toctree
- Adds `starting_llama_stack_server.md` to `distributions` toctree

There are some other warnings im still looking at but this PR gets rid
of most of the toctree errors
Theres also an issue with the actual distribution-codegen that I can
investigate in another PR. Opened a bug for it here #2873

docs/source/providers/datasetio/index.md

@@ -1,7 +1,15 @@
-# Datasetio Providers
+# Datasetio 
+
+## Overview
 
 This section contains documentation for all available providers for the **datasetio** API.
 
-- [inline::localfs](inline_localfs.md)
-- [remote::huggingface](remote_huggingface.md)
-- [remote::nvidia](remote_nvidia.md)
+## Providers
+
+```{toctree}
+:maxdepth: 1
+
+inline_localfs
+remote_huggingface
+remote_nvidia
+```