Rollup of 5 pull requests

[matthiaskrgr]

Successful merges:

• Remove rustc::existing_doc_keyword lint #134202 (Remove rustc::existing_doc_keyword lint)
• Handle fndef rendering together with signature rendering #134354 (Handle fndef rendering together with signature rendering)
• Use links to edition guide for edition migrations #134368 (Use links to edition guide for edition migrations)
• Check for array lengths that aren't actually usize #134371 (Check for array lengths that aren't actually usize)
• An octuple of polonius fact generation cleanups #134378 (An octuple of polonius fact generation cleanups)

Failed merges:

• Rename rustc_mir_build::build to builder #134365 (Rename rustc_mir_build::build to builder)

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