Allow passing compiled queries or operation nodes to methods that accept expressions.

[igalklebanov]

Hey 👋

A further evolution of the concepts described in https://kysely.dev/docs/recipes/splitting-query-building-and-execution would be to allow passing compiled queries or operation nodes to not-yet-compiled Kysely queries.

This would allow consumption of shared "off the shelf" query "fragments", that might be pre-compiled at build time, from other services or packages (including external ones).