Modular manager references

[simolus3]

The manager templates used to disable generating a typed reference class when modular code-generation was enabled, instead referring to the general BaseReferences class in the runtime package.

This adds support for that feature by resolving the modular-specific issues (like referring to typedefs and classes by their imported name if needed).

This is tested by the modular package which can now use that feature. But @dickermoshe it would be helpful if you could take a quick look to make sure I didn't miss anything.

Closes #3398.

[github-actions]

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[dickermoshe]

Looks great.

I think we should add tests so that all manager tests are also ran on modular code.

btw, when using the manager it's really helpful to do modular generation because otherwise the generic is private (_$AppDatabase) so I'm pumped about this

[simolus3]

I think we should add tests so that all manager tests are also ran on modular code.

This is tricky to pull off without copy-pasting all the tests and keeping them in sync 🤔 After all, we'd have to run both the default and the modular builder on the same database definitions, but they would generate separate and independent manager classes.

As a first step, I've added a simple test to the modular package.

[dickermoshe]

If you feel the testing is sufficient.
btw, with the status on this PR #3281