Rollup merge of #74491 - xldenis:constant-binop-opt, r=oli-obk

Rollup merge of #74491 - xldenis:constant-binop-opt, r=oli-obk

Optimize away BitAnd and BitOr when possible

This PR lets `const_prop` optimize away `a | true == true` , `a & false == false` and `a * 0 = 0`. While I was writing this I've realized that constant propagation misses a lot of opportunities. For example:  https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=2a4b45e772f214210a36749b27223bb0

Constant propagation doesn't seem to... propagate constants, additionally the way constant propagation is currently setup makes it tricky to add cases like `a | false == a`.

I tried to organize `eval_rvalue_with_identities` to make the pattern of the optimizations easier to see but it still obscurs what should be a simple peephole optmization.

cc @oli-obk