Converted sentinel types to use new sentinel class

[sydduckworth]

Description

Closes #2122

• Bumped typing-extensions to 4.16
• Replaced NOT_SET and USE_INTERNAL implementation with sentinel
• Removed NotSetType and UseInternal type aliases since sentinel lets the value and type use the same name

AI Disclosure

No AI tools used.

Tasks

• run prek on your machine
• run pytest on your machine
• Does this PR add new features and / or change user-facing code / API? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • update relevant docstrings and / or docs/ page
  • for any new features, add unit tests

news fragment change types...

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: bug fix
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.general.rst: infrastructure or miscellaneous change

[braingram]

Thanks for making the updates. The use of sentinel helps to clean up the code.

Would you open an issue to track that we can use the builtin sentinel once our minimum python version is 3.15?

[sydduckworth]

Thanks for making the updates. The use of sentinel helps to clean up the code.

Would you open an issue to track that we can use the builtin sentinel once our minimum python version is 3.15?

Ruff has a linter rule (UP035) that triggers for typing-extensions imports that aren't necessary based on the project's minimum Python version.

We use several other types from typing-extensions in other parts of the codebase so idk if I'd want to manually track them for different versions.

[braingram]

Thanks for pointing out the rule. The description says:

This rule thus avoids flagging imports from typing_extensions in such cases.

Testing by setting the ruff version to 3.15 it doesn't update sentinel (or report a rule violation). Perhaps the rule doesn't include sentinel yet. An issue seems more straightforward than relying on some ruff rule to be updated. #2132