Update InlineTypedDict Implementation to conform to PEP 764 Specification

[DanieleIsoni]

Feature

Align the experimental InlineTypedDict feature with the PEP 764 specification.

Pitch

The current experimental InlineTypedDict syntax in mypy allows for concise inline TypedDict definitions, but it does not fully conform to the PEP 764. Updating this feature to adhere to PEP 764 would ensure consistency with the official Python typing standards and enhance compatibility across type checkers and codebases.

Example of the PEP 764 syntax:

def func(n: str, y: int) -> TypedDict[{"name": str, "year": int}]:
    return {"name": n, "year": y}

[JelleZijlstra]

From offline discussion with @ilevkivskyi, we're OK adding support for the PEP 764 syntax but we'd like to keep the existing syntax as a mypy-specific extension.