Use more principled check for generics in const ops Fixes rust-lang/rust#144547. Fixes rust-lang/rust#140891. In the future, we likely want to make the check less likely to be missed by reducing the number of external entry points to HIR type lowering. Note: If this causes pass->error regressions (not truly regressions because those cases were mistakenly accepted), they can easily be avoided for the time being by only running the check if `is_self_alias` is true or mgca is enabled. - **Fix parsing of mgca const blocks in array repeat exprs** - **Use more principled check for generics in const ops**