[ty] Add a dedicated diagnostic for TypedDict deletions (#22123)
## Summary
Provides a message like:
```
error[invalid-argument-type]: Cannot delete required key "name" from TypedDict `Movie`
--> test.py:15:7
|
15 | del m["name"]
| ^^^^^^
|
info: Field defined here
--> test.py:4:5
|
4 | name: str
| --------- `name` declared as required here; consider making it `NotRequired`
|
info: Only keys marked as `NotRequired` (or in a TypedDict with `total=False`) can be deleted
```
