Rename proto package to protobuf

[philippgille]

While both terms are commonly used to refer to protocol buffers, "protobuf" might be a bit more formal and recognizable, for example because the official website for protocol buffers is https://protobuf.dev/, the main repo is https://github.com/protocolbuffers/protobuf, and the Go library is https://github.com/protocolbuffers/protobuf-go, where they use the tag protobufs but not proto.

While in their Go library the main package that's used when working with protocol buffers is still the proto one at https://pkg.go.dev/google.golang.org/protobuf/proto, I think "protobuf" is still the more recognizable one when referring to the encoding as a whole.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (918b014) 63.64% compared to head (d68f94b) 63.64%.

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Additional details and impacted files

@@           Coverage Diff           @@
##           master     #171   +/-   ##
=======================================
  Coverage   63.64%   63.64%           
=======================================
  Files          25       25           
  Lines        2107     2107           
=======================================
  Hits         1341     1341           
  Misses        651      651           
  Partials      115      115           

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