kafkacat: enable support for deserializing Avro message

[benesch]

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This required the addition of a new formula, libserdes, which is included in the first commit in this PR.

[fxcoudert]

Duplicate of #44391

[benesch]

Hmm, not quite, #44391 incorrectly lists librdkafka as a dependency of libserdes. I'll submit a PR to fix that up.

[benesch]

#48353

[peoplemerge]

@benesch I don't really grok the build process, but it doesn't seem like this has landed as a binary yet. You would hope it would after 2 weeks.
brew up && brew install kafkacat seems to be downloading a binary that lacks this improvement:
kafkacat --version 2>&1 |grep avro should display the avro improvements.

That said, brew install --build-from-source kafkacat works fine and has our patches. Ideas?

[benesch]

I think we need to add a revision 1 line to the kafkacat formula, or the bottles won't be rebuilt until a new version of kafkacat is added to Homebrew. I'm not positive, though. @fxcoudert can you advise?