rustc: Inline bitwise modification operators

These need to be inlined across crates to avoid showing up as one-instruction
functions in profiles! In the benchmark from #43578 this decreased the
translation item collection step from 30s to 23s, and looks like it also allowed
vectorization elsewhere of the operations!

src/librustc_data_structures/bitslice.rs

@@ -134,9 +134,11 @@ pub trait BitwiseOperator {
 
 pub struct Union;
 impl BitwiseOperator for Union {
+    #[inline]
     fn join(&self, a: usize, b: usize) -> usize { a | b }
 }
 pub struct Subtract;
 impl BitwiseOperator for Subtract {
+    #[inline]
     fn join(&self, a: usize, b: usize) -> usize { a & !b }
 }