[match-case] fix matching against typing.Callable and Protocol types.

[randolf-scholz]

(Explain how this PR changes mypy.)

• Fixes match-case class checking against collection.abc.Callable raises error [misc] #14014
• Partially Fixes [match-case]/[isinstance] narrowing logic against the special AnyCallable Protocol differs from callable() check #19470
• Added new tests testMatchClassPatternCallable, testMatchClassPatternProtocol and testMatchClassPatternCallbackProtocol
• Fixed partially broken test testOverloadOnProtocol

I added an extra if-branch that checks for typing.Callable in visit_class_pattern, and an extra if-branch to handle structural types in the conditional_types function.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

strawberry (https://github.com/strawberry-graphql/strawberry)
+ strawberry/relay/types.py:849: error: Need type annotation for "v"  [var-annotated]
+ strawberry/relay/types.py:849: note: Error code "var-annotated" not covered by "type: ignore" comment
+ strawberry/relay/types.py:854: error: Argument 1 to "enumerate" has incompatible type "AsyncIterator[NodeType] | AsyncIterable[NodeType]"; expected "Iterable[Never]"  [arg-type]

prefect (https://github.com/PrefectHQ/prefect)
+ src/prefect/flows.py:1239: error: Argument 1 to "BlockStorageAdapter" has incompatible type "Union[ReadableDeploymentStorage, RunnerStorage]"; expected "Union[ReadableDeploymentStorage, WritableDeploymentStorage]"  [arg-type]
+ src/prefect/flows.py:1353: error: Argument 1 to "BlockStorageAdapter" has incompatible type "Union[ReadableDeploymentStorage, RunnerStorage]"; expected "Union[ReadableDeploymentStorage, WritableDeploymentStorage]"  [arg-type]
+ src/prefect/tasks.py:945: error: Incompatible return value type (got "Coroutine[Any, Any, TaskRun]", expected "TaskRun")  [return-value]
+ src/prefect/tasks.py:945: note: Maybe you forgot to use "await"?

meson (https://github.com/mesonbuild/meson)
+ mesonbuild/compilers/mixins/clike.py:411:29: error: List item 0 has incompatible type "list[Dependency]"; expected "Dependency"  [list-item]

mitmproxy (https://github.com/mitmproxy/mitmproxy)
+ mitmproxy/http.py:607: error: Unused "type: ignore" comment  [unused-ignore]

xarray (https://github.com/pydata/xarray)
+ xarray/core/dataset.py: note: In member "drop_vars" of class "Dataset":
+ xarray/core/dataset.py:5796: error: Argument 1 to "set" has incompatible type "Iterable[Hashable]"; expected "Iterable[Iterable[Hashable]]"  [arg-type]
+ xarray/core/dataset.py:5798: error: Argument 1 to "_assert_all_in_dataset" of "Dataset" has incompatible type "set[Iterable[Hashable]]"; expected "Iterable[Hashable]"  [arg-type]
+ xarray/core/dataset.py:5803: error: No overload variant of "get" of "dict" matches argument types "Iterable[Hashable]", "None"  [call-overload]
+ xarray/core/dataset.py:5803: note: Possible overload variants:
+ xarray/core/dataset.py:5803: note:     def get(self, Hashable, None = ..., /) -> Index | None
+ xarray/core/dataset.py:5803: note:     def get(self, Hashable, Index, /) -> Index
+ xarray/core/dataset.py:5803: note:     def [_T] get(self, Hashable, _T, /) -> Index | _T
+ xarray/core/dataset.py:5806: error: Argument 1 to "set" has incompatible type "set[Iterable[Hashable]]"; expected "Iterable[Hashable]"  [arg-type]
+ xarray/core/dataset.py:5809: error: Argument 1 to "set" has incompatible type "set[Hashable]"; expected "Iterable[Iterable[Hashable]]"  [arg-type]
+ xarray/core/dataset.py:5816: error: Argument 2 to "assert_no_index_corrupted" has incompatible type "set[Iterable[Hashable]]"; expected "set[Hashable]"  [arg-type]
+ xarray/core/dataset.py: note: In member "drop_dims" of class "Dataset":
+ xarray/core/dataset.py:6102: error: Argument 1 to <set> has incompatible type "str | Iterable[Hashable]"; expected "Hashable"  [arg-type]
+ xarray/core/dataset.py: note: At top level:
+ xarray/core/datatree.py: note: In member "drop_nodes" of class "DataTree":
+ xarray/core/datatree.py:1133: error: Argument 1 to <set> has incompatible type "str | Iterable[str]"; expected "str"  [arg-type]
+ xarray/backends/api.py: note: In function "to_netcdf":
+ xarray/backends/api.py:1973: error: List item 0 has incompatible type "Iterable[Hashable]"; expected "Hashable"  [list-item]
+ xarray/backends/api.py: note: At top level:
+ xarray/computation/fit.py: note: In function "curvefit":
+ xarray/computation/fit.py:407: error: List item 0 has incompatible type "str | DataArray | Iterable[str | DataArray]"; expected "str | DataArray"  [list-item]

graphql-core (https://github.com/graphql-python/graphql-core)
+ tests/execution/test_subscribe.py:292: error: Unused "type: ignore" comment  [unused-ignore]

websockets (https://github.com/aaugustin/websockets)
+ src/websockets/legacy/server.py:368: error: Incompatible return value type (got "Awaitable[tuple[HTTPStatus | int, Headers | Mapping[str, str] | Iterable[tuple[str, str]] | SupportsKeysAndGetItem, bytes] | None]", expected "tuple[HTTPStatus | int, Headers | Mapping[str, str] | Iterable[tuple[str, str]] | SupportsKeysAndGetItem, bytes] | None")  [return-value]
+ src/websockets/legacy/server.py:368: note: Maybe you forgot to use "await"?
+ src/websockets/legacy/server.py:591: error: Incompatible types in assignment (expression has type "Coroutine[Any, Any, tuple[HTTPStatus | int, Headers | Mapping[str, str] | Iterable[tuple[str, str]] | SupportsKeysAndGetItem, bytes] | None]", variable has type "tuple[HTTPStatus | int, Headers | Mapping[str, str] | Iterable[tuple[str, str]] | SupportsKeysAndGetItem, bytes] | None")  [assignment]
+ src/websockets/legacy/server.py:591: note: Maybe you forgot to use "await"?