[OpenLineage] docs: Update whole OpenLineage Provider docs.

[kacpermuda]

The OpenLineage Provider docs needed some refreshment.

I went through current docs and tried to find anything that is outdated, validated already provided information against the actual code and tried to add some new useful information. Some part added to the docs are sourced from current OL Airflow integration docs on OL website, but they have been updated to work for the provider package. I believe it's the right direction to keep everything here, as we may want to remove OL website docs on Airflow integration in the future, as it's mostly living in the provider package.

I also simplified the Menu structure, so it's easier to find everything and it's not as nested as before.

Let me know what You think, if there is something missing, misleading, not clear enough etc. Any feedback is highly appreciated.

How to view the new docs ?

The easiest way is to use BREEZE and run:

breeze build-docs --package-filter apache-airflow-providers-openlineage --clean-build

then You can run the server with:

 sh docs/start_doc_server.sh

and view the docs at localhost

Next steps

I think we need a new version of this image, with provider instead of openlineage-airflow, included on the Intro page. I will try to update it, and as soon as we host it somewhere, we can do the switch.

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[dirrao]

LGTM. I would request open lineage expert look into this.

[JDarDagran]

Overall, I love the changes. Very well done 🚀 Added some minor comments.