SDK allows invalid protobuf string

[fmorency]

I reported #22414 last year and would like to continue the discussion.

TL;DR: The protobuf library used by CosmosSDK (gogoproto) doesn't enforce UTF-8 check on string. This behavior breaks the Protobuf specification and upstream projects, e.g., Yet Another Cosmos Indexer, relying on the official Go protobuf library.

I still believe this is wrong and would like to discuss a migration path towards enabling this check and conforming to the protobuf specification.