Upgrade SQLAlchemy to v2

[smotornyuk]

When CKAN v2.11 is out and its code is completely compatible with SQLAlcheny v2, extension maintainers can start upgrading their extensions. I'll add a page to the wiki with upgrade tips.

As for the core, we can now upgrade to SQLAlchemy v2. The main part of this upgrade includes only changes to the version inside the requirements file. It's enough to install the latest SQLAlchemy and nothing will be broken.

But v2 of SQLAlchemy also includes built-in type-definition, so we no longer need any mypy or sqlalchemy-stubs addons. So the secondary feature of this PR is making our typing compatible with new types definitions.

ℹ️ When upgrading CKAN locally, you have to remove external type definitions, or they will cause incorrect type detection. Run pip uninstall -y sqlalchemy2-stubs sqlalchemy-stubs

For anyone who is going to review this PR, here are the most common types of changes:

• instead of == False it's better to use == false(). The result is the same, but the latter is accepted by linters. I changed this expression only inside files that were changed due to other reasons.
• model.Session.query is properly typed now, so we don't need explicit types when assigning its result into a variable. x: Query[...] = model.Session.query(...) transformed into x = model.Session.query(...)
• model.Session.query now always returns a sequence of the Row object. list[tuple[TYPE]] transformed into Sequence[Row[tuple[TYPE]]]. Sometimes list is used instead of the Sequence, to reduce number of changes. But for new code it's recommended to use Sequence.
• .as_mutable(JSONB) - this type signature is not yet completed and requires # type: ignore comment
• Whenever model's classmethod returns Self, .query(cls) must be used instead of static form, like .query(Tag), because Tag class is not final and can be extended by child class
• pgcode property exists in SQLAlchemy exceptions only when working with PostgreSQL. Type checker doesn't know that we are not going to use other DB engines, so any access to pgcode must be wrapped into a typecast expression.

[amercader]

@wardi @smotornyuk I merged master and got a lot of scary typing failures that luckily went away after adapting the tracking model definition (6325fa4)

This PR looks good to me. I think it would be good to merge this and start working with it on master going forward to identify potential issues way ahead of a 2.12 release.

[amercader]

@wardi @smotornyuk ping any objections to merge this?

[smotornyuk]

Nothing here, I finished all the things I planned for this PR. There are a number of improvements that can be done with new version of SQLalchemy, but I'd like to make them in a separate PR, to avoid blocking this dependency upgrade