Rollup merge of #148716 - camelid:finish-type_const, r=BoxyUwU

mgca: Finish implementation of `#[type_const]`

tracking issue: rust-lang/rust#132980
fixes rust-lang/rust#140729
fixes rust-lang/rust#140860

- **Fix `#[type_const]` attribute placement validation**
- **Perform WF-checking on type_const RHS's**
- **Check type_const type is ConstParamTy_ and that RHS matches it**
- **Check that impls of `#[type_const]` consts also have the attr**

r? ```@BoxyUwU```

Author: matthiaskrgr