Reorganize Masonry modules

[PoignardAzur]

No description provided.

[PoignardAzur]

First commit just moves modules around and adds temporary re-exports in lib.rs to avoid changing too many files.

[PoignardAzur]

This PR was executed in roughly four steps:

• Run cargo +nightly fmt with imports_granularity = "Item"
• Move items, files and modules around to get the desired structure.
• Use a lot of sed commands to bulk-change import directives to point to the right modules.
• Run cargo +nightly fmt with imports_granularity = "Module" to restore the previous structure.

In theory there shouldn't be any code changes, though in practice I can't guarantee it.

[jaredoconnell]

If we want to approve this design, I don't see any issues. Daniel suggested splitting a few things up, so it's worth considering that, too.