Rollup of 12 pull requests

[Zalathar]

Successful merges:

• Fix -Zremap-path-scope rmeta handling #139550 (Fix -Zremap-path-scope rmeta handling)
• Consistent trait bounds for ExtractIf Debug impls #139764 (Consistent trait bounds for ExtractIf Debug impls)
• Implement Iterator::last for vec::IntoIter #139773 (Implement Iterator::last for vec::IntoIter)
• Implement RFC 3503: frontmatters #140035 (Implement RFC 3503: frontmatters)
• coverage-dump: Resolve global file IDs to filenames #140251 (coverage-dump: Resolve global file IDs to filenames)
• std: get rid of sys_common::process #140393 (std: get rid of sys_common::process)
• Fix RustAnalyzer discovery of rustc's stable_mir crate #140532 (Fix RustAnalyzer discovery of rustc's stable_mir crate)
• Steer docs to utf8_chunks and Iterator::take #140598 (Steer docs to utf8_chunks and Iterator::take)
• Use more accurate ELF flags on MIPS #140634 (Use more accurate ELF flags on MIPS)
• Clean rustdoc tests folder #140673 (Clean rustdoc tests folder)
• Be a bit more relaxed about not yet constrained infer vars in closure upvar analysis #140678 (Be a bit more relaxed about not yet constrained infer vars in closure upvar analysis)
• Update mdbook to 0.4.49 #140687 (Update mdbook to 0.4.49)

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