Investigate a sqlc Java backend

[stuartwdouglas]

We should investigate a sqlc backend for Java, there is a simple Kotlin one here: https://github.com/sqlc-dev/sqlc-gen-kotlin

[alecthomas]

That looks like a good start, but I think we'll need to write FTL-specific code generators, as we'll need to generate queries that are "verbs" rather than normal functions.

[stuartwdouglas]

We could make the code generation add additional metadata to the generated code, that could then be picked up by schema generation.