codegen: consider generating wrappers on format enums for shared variant methods

As in, if there are multiple formats for a table, but those formats share some set of methods, we should generate a method on the enum that forwards the call to each of those variants.

We could also get fancier here and generate methods on the wrapper even when only one variant has the method, and make it return `None`? But that feels like it could get noisy. In that case, we could consider adding an annotation that would be added to specific methods on a variant which would cause us to generate a a method call on the enum (e.g. make this opt-in, in the case where not all variants have a method)

see #682 for an example of the code this would save us hand-writing.

Start by reviewing issue #682 to understand the hand-written wrapper methods this code generation could replace, then locate the existing format-enum code generation path. Define how methods shared by all variants should be forwarded, and resolve whether methods present on only one variant need opt-in annotations. Done means the generator produces the intended wrappers with coverage for the selected behavior.

Written by the indexing model from the issue text.