Do not type DeclarativeContainer.__getattr__ as returning a Provider (#910)

[uttam12331]

Summary

Closes #910.

The container type stub declares

class Container:
    ...
    def __getattr__(self, name: str) -> Provider[Any]: ...

on the base Container, so DeclarativeContainer inherits a catch-all __getattr__. That makes type checkers accept access to any attribute on a declarative container as a Provider, silently hiding typos and references to providers that were never declared:

class Container(containers.DeclarativeContainer):
    service = providers.Factory(Service)

c = Container()
c.serivce  # typo — no type error today, inferred as Provider[Any]

As noted in the issue, this only makes sense for DynamicContainer, whose providers are added by name at runtime — not for DeclarativeContainer, whose providers are declared statically.

Change

Move the __getattr__ stub from the base Container to DynamicContainer. Now:

• DeclarativeContainer exposes only its statically declared providers → accessing an undeclared attribute is flagged.
• DynamicContainer keeps resolving arbitrary attributes to Provider[Any].

Verified with mypy --strict:

class C(containers.DeclarativeContainer):
    provider = providers.Factory(int)

C().provider       # ok: Factory[int]
C().nonexistent    # error: "C" has no attribute "nonexistent"   <-- previously silent

containers.DynamicContainer().anything   # ok: Provider[Any]

Tests

mypy --strict tests/typing passes (19 source files). Added Test 7 in tests/typing/dynamic_container.py asserting that dynamic attribute access still resolves to providers.Provider[Any], so the DynamicContainer behavior stays covered. The existing declarative_container.py typing tests continue to pass because they access explicitly declared providers.