Rollup merge of #48565 - alexcrichton:rename-bmi, r=cramertj
Rollup merge of #48565 - alexcrichton:rename-bmi, r=cramertj

rustc: Rename `bmi` feature to `bmi1`

This is what [Intel calls it][bmi1] and will [remove a special case][stdsimd]
when verifying intrinsics in stdsimd.

[bmi1]: https://software.intel.com/sites/landingpage/IntrinsicsGuide/#othertechs=BMI1
[stdsimd]: https://github.com/rust-lang-nursery/stdsimd/blob/bed25b2a9f3b28e6ea80de6d87842f739a2e2d58/crates/stdsimd-verify/tests/x86-intel.rs#L252-L258

GBGamer/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust