Add plugable handler for `CREATE FUNCTION`

[milenkovicm]

Which issue does this PR close?

Closes #9332.

Rationale for this change

explained in #9332

What changes are included in this PR?

this is minimum viable product, with some open question which i hope to resolve in the process of PR review (note TODOs)

Are these changes tested?

There is a test in place but would add more if community aggress to accept the change. Usage example can be found at https://github.com/milenkovicm/torchfusion

Are there any user-facing changes?

There are using facing changes, but they are backward compatible. Would update docs if community aggress to accept the change