Remove type checker-specific symbols from builtins.pyi and typing.pyi

I'm working to get rid of the type checker-specific symbols that currently are in our core stubs but don't exist at runtime. I'll use this issue to track the work needed. This involves changes both to typeshed and to type checkers.

Affected names:

• typing._TypedDict. Suggesting to rename to _typeshed.TypedDictFallback. (mypy and pyright)
• typing._promote -> _typeshed._promote (mypy only)
• typing.AwaitableGenerator -> _typeshed.AwaitableGenerator (mypy and pyright)
• builtins.function (mypy and pyright). Need to look more into why we can't just use types.FunctionType.
  • Working on this in mypy but it requires updating a ton of test cases
• builtins.ellipsis (mypy and pyright). Should add a new name to _typeshed, similar to NoneType.

builtins.module was also mentioned in the past but it's been fixed already (mypy PR: https://github.com/python/mypy/pull/3107).

Linked issues and PRs:

• #2999
• #3556
• #3932
• python/mypy#11564
• python/mypy#8240
• https://github.com/python/mypy/issues/2765
• https://github.com/python/mypy/issues/8699

Start with builtins.pyi and typing.pyi, then review the linked typeshed and type-checker issues to understand the required replacements. Check the affected mypy and pyright behavior and test cases, especially the builtins.function cases. Done means the type-checker-specific symbols are removed from the core stubs and the affected type-checker tests pass.