Auto merge of #154300 - JonathanBrouwer:rollup-MkFxTPv, r=JonathanBrouwer

Rollup of 4 pull requests

Successful merges:

 - rust-lang/rust#153434 (Use a safe `BucketIndex` abstraction in `VecCache`)
 - rust-lang/rust#154133 (Defer codegen for the VaList Drop impl to actual uses)
 - rust-lang/rust#154297 (fix/extend some mir-opt comments)
 - rust-lang/rust#154299 (document some functions on AttributeExt)