Auto merge of #150519 - camelid:mgca-forbid-params-properly, r=BoxyUwU

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**