community[patch]: import flattening fix (#20110)

This PR should make it easier for linters to do type checking and for IDEs to jump to definition of code.

See #20050 as a template for this PR.
- As a byproduct: Added 3 missed `test_imports`.
- Added missed `SolarChat` in to __init___.py Added it into test_import
ut.
- Added `# type: ignore` to fix linting. It is not clear, why linting
errors appear after ^ changes.

---------

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

libs/community/langchain_community/cache.py

@@ -1998,7 +1998,7 @@ class AzureCosmosDBSemanticCache(BaseCache):
             k=1,
             kind=self.kind,
             ef_search=self.ef_search,
-            score_threshold=self.score_threshold,
+            score_threshold=self.score_threshold,  # type: ignore[arg-type]
         )
         if results:
             for document in results: