Auto merge of #92592 - Mark-Simulacrum:beta-next, r=Mark-Simulacrum
[beta] backports
Backports these PRs:
* Fix HashStable implementation on InferTy #91892
* Revert setting a default for the MACOSX_DEPLOYMENT_TARGET env var for linking #91870
* Make rustdoc headings black, and markdown blue #91534
* Disable LLVM newPM by default #91190
* Deduplicate projection sub-obligations #90423
* Sync portable-simd to remove autosplats #91484 by dropping portable_simd entirely (keeping the subtree, just from std/core)
* Quote bat script command line #92208
* Fix failing tests #92201 (CI fix)
r? `@Mark-Simulacrum`
