errors: migrate from gogo/protobuf to google.golang.org/protobuf

[liran-funaro]

github.com/gogo/protobuf, along with the related github.com/gogo/status and github.com/gogo/googleapis, is deprecated and unmaintained. This migrates the whole module to the standard, maintained protobuf stack it already depended on: google.golang.org/protobuf (+ anypb), google.golang.org/grpc/status, and
google.golang.org/genproto/googleapis/rpc/status.

The .proto files are regenerated with the standard protoc-gen-go and protoc-gen-go-grpc, dropping the custom protoc-gen-gogoroach plugin and all gogoproto options, and the hand-written code is adapted to the v2 runtime:

• errbase packs and unpacks error detail payloads with anypb.New and (*anypb.Any).UnmarshalNew, resolving types through the standard protoregistry instead of gogo's registry.
• The previously non-nullable embedded fields (Details, Cause, ErrorTypeMark) are now pointers, read through the generated nil-safe getters. DecodeError takes *EncodedError and GetTypeMark returns *errorspb.ErrorTypeMark accordingly.
• extgrpc and grpc/middleware use google.golang.org/grpc/status. Because the standard Any can hold standard protobufs directly, the former gogo/standard status split collapses into a single path, and google.rpc.Status now comes from genproto with the same type URL.
• go.mod drops all three gogo modules.

Wire compatibility is preserved: no proto package/message name or field number changes, and google.protobuf.Any type URLs are unchanged, so errors serialized by the previous gogo-based version still decode here and vice versa.

This is a breaking API change (major version): the encoder/decoder registration interfaces now reference the v2 proto.Message, so consumers that register custom error types must supply standard-protobuf payloads. Errors originally produced as github.com/gogo/status types decode to an opaque error (message and safe details preserved) rather than being reconstructed as a gRPC status.

• resolves Gogoprotobuf replacement #138

[cockroachlabs-cla-agent]

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