Protobuf well-known types unnecessarily generated

[mzabaluev]

Description

The proto compiler enables the compile_well_known_types setting in prost-build configuration, and the generated google.protobuf.rs content is included into tendermint-proto under the google::protobuf path, with the exception of Duration and Timestamp that get special manually maintained struct definitions. In fact, no other well-known types are referenced by any proto message definitions in Tendermint, so the generated content is unnecessary. Additionally, since the WKT definitions are provided with the compiler, this creates a subtle dependency on the protoc compiler installation that may result in "jitter" in the public tendermint-proto API.

Definition of "done"

The generated structs are removed from google::protobuf, only Duration and Timestamp are left to be manually maintained (pending resolution of #1053).