Recover upon mistyped error on typo'd `const` in const param def
And add machine-applicable fix for the typo'd `const` keyword.
### Before
```
error: expected one of `,`, `:`, `=`, or `>`, found `N`
--> src/lib.rs:1:18
|
1 | pub fn bar<Const N: u8>() {}
| ^ expected one of `,`, `:`, `=`, or `>`
```
### After This PR
```
error: `const` keyword was mistyped as `Const`
--> test.rs:1:8
|
1 | fn bar<Const N: u8>() {}
| ^^^^^
|
help: use the `const` keyword
|
1 | fn bar<const N: u8>() {}
| ~~~~~
```
Fixes#111941.
45ca2f732e