Minor improvements in collections.pyx

Minor improvements in collections.pyx

### Description

This PR introduces minor improvements to collections.pyx:

* Adds missed type annotations yielding slightly more optimised code
* Adds missed `cpdef` methods used internally
* Marks private methods with `@cython.final`

Fixes #9477

### Checklist
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This pull request is:

- [ ] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [X] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [ ] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

**Have a nice day!**

Closes: #9478
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/9478
Pull-request-sha: c006c76c2c50491ea1be9c723c278da16c151397

Change-Id: I74b3df2bc790db49e331b8f8085c797249364b07