devel/protobuf: Update to 29.3

[michaelo]

Summary

Approved by: jrm (mentor), otis (mentor), sunpoet (maintainer)
Release Notes: https://github.com/protocolbuffers/protobuf/releases/tag/v29.3

[jrm]

Looks good, but we should also hear from @sunpoet. (That's always implied when I approve changes to a port someone else maintains.)

[michaelo]

In D48669#1110019, @jrm wrote:

Looks good, but we should also hear from @sunpoet. (That's always implied when I approve changes to a port someone else maintains.)

Waiting for as well.

[sunpoet]

This patch is incomplete.

I've already done the update with protobuf 29.3 update, PORTREVISION bump of dependent ports (adfb8194d132295d00880bf84675be78bbff09ec) and fix several ports (77c322e53c89bd684caca130d54a9b6b457aa8ef, 68b882ac1f0c83b87b6fb45fa0c533a5e3fcb64b and 1f7798494f5e8daf1ad47fac68bf39c174b64fab).