Cleanup Render Pipeline menu script entry

[sebastienlagarde]

Purpose of this PR

This PR cleanup the Edit > Render Pipeline menu which were full of obsolete menu + update the documentation accordingly.

New menu:

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Testing status

Manual Tests: What did you do?

• Opened test project + Run graphic tests locally
• Built a player
• Checked new UI names with UX convention
• Tested UI multi-edition + Undo/Redo + Prefab overrides + Alignment in Preset
• C# and shader warnings (supress shader cache to see them)
• Checked new resources path for the reloader (in developer mode, you have a button at end of resources that check the paths)
• Other:

Automated Tests: What did you setup? (Add a screenshot or the reference image of the test please)

Yamato: (Select your branch):
https://yamato.prd.cds.internal.unity3d.com/jobs/902-Graphics

Any test projects to go with this to help reviewers?

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Comments to reviewers

Notes for the reviewers you have assigned.

[sebastienlagarde]

Note: I noticed that export Sky to texture don't always work.
Also this menu isn't documented in our documentation, we should add one (cc @JordanL8 ).

Merging before hackweek but feel free to add feedback.