Add a way to implicitly create declarations, potentially from resolve

[Ekrekr]

We've been discussing this as part of new features for v3.0.0 - this could be a format that one of the utility functions could take:

implicitResolve({database, schema, name}}, which creates a declaration if it does not exist.

[BenBirt]

"If it does not exist" is tricky - it can only really work if the function is only callable in a Contextable context (i.e. it can't be callable from "normal" JS). This is because we don't know what exists or what doesn't until all non-Contextable JS has been executed. (As an aside, it is for this reason that inline tables never really worked.)

But Contextable functions are not (currently) expected to be able to add nodes to the DAG. We'd have to be careful to ensure that actually makes sense / ordering constraints are preserved.