Mark SQLAlchemy stubs with ignore_missing_stub = false

[Avasam]

Follow-up to #9596 (keeping as draft until that one is merged)
Mostly used stubgen for the missing types. Except for stubs/SQLAlchemy/sqlalchemy/sql/annotation.pyi which had to be done manually.

Changes to imports:

• Standardize relative vs absolute imports (this stub seems to prefer relative imports)
• Prefer importing directly from the source module, rather than using re-exports (which was often needed for the next point)
• Update imports to work around "pytype.pytd.visitors.ContainerError: Conflicting values for TypeVar" when parsing SQLAlchemy stubs created by stubgen google/pytype#1087
• Allowlist various compat module re-exports

There's still a pytype issue I'm not certain about.

[Avasam]

I don't understand what this Pytype error is trying to tell me. Other than that, this PR is ready to be looked at.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉