…r=BoxyUwU

Disentangle `ForwardGenericParamBan` and `ConstParamTy` ribs

In rust-lang#137617, the `ConstParamTy` rib was adjusted to act kinda like the `ForwardGenericParamBan`. However, this means that it no longer served its purpose banning generics from *parent items*. Although we still are checking for param type validity using the `ConstParamTy_` trait, which means that we weren't accepting code we shouldn't, I think it's a bit strange for us not to be rejecting code like this during *resolution* and instead letting these malformed const generics leak into the type system:

```rust
trait Foo<T> {
  fn bar<const N: T>() {}
}
```

This PR does a few things:
1. Introduce a `ForwardGenericParamBanReason` enum, and start using the `ForwardGenericParamBan` rib to ban forward-declared params in const tys when `generic_const_parameter_types` is enabled.
2. Start using the `ConstParamTy` rib to ban *all* generics when `generic_const_parameter_types` is disabled.
3. Improve the diagnostics for both of the cases above, and for forward-declared params in parameter defaults too :3

r? `@BoxyUwU` or reassign

…earth

Rollup of 12 pull requests

Successful merges:

 - rust-lang#134076 (Stabilize `std::io::ErrorKind::InvalidFilename`)
 - rust-lang#137504 (Move methods from Map to TyCtxt, part 4.)
 - rust-lang#138175 (Support rmeta inputs for --crate-type=bin --emit=obj)
 - rust-lang#138259 (Disentangle `ForwardGenericParamBan` and `ConstParamTy` ribs)
 - rust-lang#138280 (fix ICE in pretty-printing `global_asm!`)
 - rust-lang#138318 (Rustdoc: remove a bunch of `@ts-expect-error` from main.js)
 - rust-lang#138331 (Use `RUSTC_LINT_FLAGS` more)
 - rust-lang#138357 (merge `TypeChecker` and `TypeVerifier`)
 - rust-lang#138394 (remove unnecessary variant)
 - rust-lang#138403 (Delegation: one more ICE fix for `MethodCall` generation)
 - rust-lang#138407 (Delegation: reject C-variadics)
 - rust-lang#138409 (Use sa_sigaction instead of sa_union.__su_sigaction for AIX)

r? `@ghost`
`@rustbot` modify labels: rollup

…earth

Rollup of 12 pull requests

Successful merges:

 - rust-lang#134076 (Stabilize `std::io::ErrorKind::InvalidFilename`)
 - rust-lang#137504 (Move methods from Map to TyCtxt, part 4.)
 - rust-lang#138175 (Support rmeta inputs for --crate-type=bin --emit=obj)
 - rust-lang#138259 (Disentangle `ForwardGenericParamBan` and `ConstParamTy` ribs)
 - rust-lang#138280 (fix ICE in pretty-printing `global_asm!`)
 - rust-lang#138318 (Rustdoc: remove a bunch of `@ts-expect-error` from main.js)
 - rust-lang#138331 (Use `RUSTC_LINT_FLAGS` more)
 - rust-lang#138357 (merge `TypeChecker` and `TypeVerifier`)
 - rust-lang#138394 (remove unnecessary variant)
 - rust-lang#138403 (Delegation: one more ICE fix for `MethodCall` generation)
 - rust-lang#138407 (Delegation: reject C-variadics)
 - rust-lang#138409 (Use sa_sigaction instead of sa_union.__su_sigaction for AIX)

r? `@ghost`
`@rustbot` modify labels: rollup

…earth

Rollup of 12 pull requests

Successful merges:

 - rust-lang#134076 (Stabilize `std::io::ErrorKind::InvalidFilename`)
 - rust-lang#137504 (Move methods from Map to TyCtxt, part 4.)
 - rust-lang#138175 (Support rmeta inputs for --crate-type=bin --emit=obj)
 - rust-lang#138259 (Disentangle `ForwardGenericParamBan` and `ConstParamTy` ribs)
 - rust-lang#138280 (fix ICE in pretty-printing `global_asm!`)
 - rust-lang#138318 (Rustdoc: remove a bunch of `@ts-expect-error` from main.js)
 - rust-lang#138331 (Use `RUSTC_LINT_FLAGS` more)
 - rust-lang#138357 (merge `TypeChecker` and `TypeVerifier`)
 - rust-lang#138394 (remove unnecessary variant)
 - rust-lang#138403 (Delegation: one more ICE fix for `MethodCall` generation)
 - rust-lang#138407 (Delegation: reject C-variadics)
 - rust-lang#138409 (Use sa_sigaction instead of sa_union.__su_sigaction for AIX)

r? `@ghost`
`@rustbot` modify labels: rollup