[SPARK-33002][PYTHON] Remove non-API annotations

### What changes were proposed in this pull request?

This PR:

- removes annotations for modules which are not part of the public API.
- removes `__init__.pyi` files, if no annotations, beyond exports, are present.

### Why are the changes needed?

Primarily to reduce maintenance overhead and as requested in the comments to #29591

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

Existing tests and additional MyPy checks:

```
mypy --no-incremental --config python/mypy.ini python/pyspark
MYPYPATH=python/ mypy --no-incremental --config python/mypy.ini examples/src/main/python/ml examples/src/main/python/sql examples/src/main/python/sql/streaming
```

Closes #29879 from zero323/SPARK-33002.

Authored-by: zero323 <mszymkiewicz@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>

Author: zero323

python/mypy.ini

@@ -32,5 +32,8 @@ ignore_missing_imports = True
 [mypy-pandas.*]
 ignore_missing_imports = True
 
-[mypy-pyarrow]
+[mypy-pyarrow.*]
+ignore_missing_imports = True
+
+[mypy-psutil.*]
 ignore_missing_imports = True

python/pyspark/_globals.pyi

@@ -16,7 +16,7 @@
 # specific language governing permissions and limitations
 # under the License.
 
-from typing import Callable, Generic, Tuple, Type, TypeVar
+from typing import Callable, Dict, Generic, Tuple, Type, TypeVar
 
 import socketserver.BaseRequestHandler  # type: ignore
 
@@ -27,6 +27,8 @@ U = TypeVar("U", bound=SupportsIAdd)
 
 import socketserver as SocketServer
 
+_accumulatorRegistry: Dict[int, Accumulator]
+
 class Accumulator(Generic[T]):
     aid: int
     accum_param: AccumulatorParam[T]

python/pyspark/accumulators.pyi

@@ -17,10 +17,12 @@
 # under the License.
 
 import threading
-from typing import Any, Generic, Optional, TypeVar
+from typing import Any, Dict, Generic, Optional, TypeVar
 
 T = TypeVar("T")
 
+_broadcastRegistry: Dict[int, Broadcast]
+
 class Broadcast(Generic[T]):
     def __init__(
         self,