Support "Protobuf Editions"

[agrue]

Protobuf Editions overview: https://protobuf.dev/editions/overview/

This feature introduces a new syntax (e.g. edition = "2023";) that currently breaks proto-lens. It crashes in this partial function here:

proto-lens/proto-lens-protoc/app/Data/ProtoLens/Compiler/Definitions.hs

Line 104 in a646710

s -> error $ "Unknown syntax type " ++ show s

The error is Unknown syntax type "editions".

[chungyc]

I have looked at this sufficiently closely by now that I know what needs to be done.

1. Update the bootstrapping generated code for the protocol buffer message types used by protoc plugins to a recent version, so that it includes the fields necessary to support Protobuf Editions. The update will not affect current behavior. This will be handled by this pull request: Catch up on changes in protobuf up to v28.0. #469

2. Update the code generator to tell protoc that it can support Protobuf Editions, which a subsequent change can do: Accept hypothetical Protobuf Editions files. #470

   Depending on the preference of the reviewers, I can modify this change to say it only supports EDITION_LEGACY, which would allow us to merge in code partially supporting Protobuf Editions early without allowing it to process Protobuf Editions files before the support is complete. Or I can make all the changes (i.e, including the subsequent steps) to support Protobuf Editions in a single much larger pull request.

3. Implement feature resolution for Protobuf Editions. This can be done with this change: Support feature resolution for Protobuf Editions. #473

4. Plumb through Protobuf Editions feature sets throughout the code generator, replacing adjustments based on syntax type with those based on feature sets. We would basically replace SyntaxType with feature sets. This can be done with this change: Use per-edition feature defaults instead of syntax type to control behavior. #477

5. Override features overridden in enclosed scopes. This can be done with this change: Override features defined in enclosed scopes. #479

These changes to the protoc plugin should be all that is necessary to support Protobuf Editions 2023, as it is limited to being a stepping stone from proto2 and proto3 to Protobuf Editions instead of adding any new functionality.