Auto merge of #135371 - Mark-Simulacrum:no-alloc-case-cmp, r=compiler-errors

Remove allocations from case-insensitive comparison to keywords

Follows up on work in 99d02fb40fd339255ed08596ebeb41e9b8a09d45, expanding the alloc-free comparisons to more cases of case-insensitive keyword matching.

r? ghost for perf

Author: bors