Move Transforms to Separate Package

[joshua-oss]

Transforms are now capable of generating metadata, which introduces a dependency between smartnoise-sql and smartnoise-synth. These packages should be able to be independently installed. A possible solution is to move transforms to a separate package and move metadata into the transforms package. Then each of the larger packages could include transforms as a dependency.

Splitting this off would be a breaking change for smartnoise-synth, because namespaces would change. It need not be a breaking change for smartnoise-sql.