[ty] Callable types are disjoint from non-callable @final nominal instance types

[InSyncWithFoo]

Summary

Resolves #513.

Callable types are now considered to be disjoint from nominal instance types where:

• The class is @final, and
• Its __call__ either does not exist or is not assignable to (...) -> Unknown.

Test Plan

Markdown tests.

[github-actions]

mypy_primer results

No ecosystem changes detected ✅

[InSyncWithFoo]

I came across this issue while working on #18294:

graphql-core (https://github.com/graphql-python/graphql-core)
- error[invalid-argument-type] src/graphql/execution/execute.py:1901:9: Argument to function `experimental_execute_incrementally` is incorrect: Expected `((Any, /) -> bool) | None`, found `bool | None | (def assume_not_awaitable(_value: Any) -> bool)`
+ error[invalid-argument-type] src/graphql/execution/execute.py:1901:9: Argument to function `experimental_execute_incrementally` is incorrect: Expected `((Any, /) -> bool) | None`, found `(bool & ((...) -> object)) | None | (def assume_not_awaitable(_value: Any) -> bool)`

[carljm]

Thank you!