Issue 44087: [sqlite3] consider adding Py_TPFLAGS_DISALLOW_INSTANTIATION to sqlite3.Statement

Currently, the sqlite3.Statement type is not exposed in the module dict:

>>> import sqlite3
>>> sqlite3.Statement
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/sqlite3/__init__.py", line 37, in __getattr__
    raise AttributeError(f"module 'sqlite3' has no attribute '{name}'")
AttributeError: module 'sqlite3' has no attribute 'Statement'


It is possible to extract it using this trick:
>>> cx = sqlite3.connect(":memory:")
>>> stmt = cx("select 1")
>>> type(stmt)
<class 'sqlite3.Statement'>
>>> type(stmt)()
<sqlite3.Statement object at 0x109006b30>

There is no use case for this; statement objects belong to the internal workings of the sqlite3 module. I suggest adding Py_TPFLAGS_DISALLOW_INSTANTIATION to make this fact more explicit.