feat(schema_registry): add support for protobuf schemas

[thalesmg]

Fixes https://emqx.atlassian.net/browse/EMQX-9470

Summary

🤖 Generated by Copilot at 8f7c584

This pull request adds support for protobuf schemas and serdes in the schema registry app, using the gpb library and dynamic module loading. It also updates the test suites, the HTTP API, the i18n file, and the build script to handle the new feature.

PR Checklist

Please convert it to a draft if any of the following conditions are not met. Reviewers may skip over until all the items are checked:

• Added tests for the changes
• Changed lines covered in coverage report
• Change log has been added to changes/{ce,ee}/(feat|perf|fix)-<PR-id>.en.md files
• For internal contributor: there is a jira ticket to track this change
• If there should be document changes, a PR to emqx-docs.git is sent, or a jira ticket is created to follow up
• Schema changes are backward compatible

Checklist for CI (.github/workflows) changes

• [na] If changed package build workflow, pass this action (manual trigger)
• [na] Change log has been added to changes/ dir for user-facing artifacts update

[thalesmg]

Talking to @zmstone , we decided to lift this restriction on gpb because it is actually LGPL and not GPLv3.

[coveralls]

Pull Request Test Coverage Report for Build 4703843216

• 54 of 61 (88.52%) changed or added relevant lines in 3 files are covered.
• 19 unchanged lines in 11 files lost coverage.
• Overall coverage increased (+0.1%) to 81.336%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
lib-ee/emqx_ee_schema_registry/src/emqx_ee_schema_registry_schema.erl	7	8	87.5%
lib-ee/emqx_ee_schema_registry/src/emqx_ee_schema_registry_serde.erl	45	51	88.24%

Files with Coverage Reduction	New Missed Lines	%
apps/emqx_bridge/src/emqx_bridge_resource.erl	1	73.5%
apps/emqx_gateway_mqttsn/src/emqx_mqttsn_channel.erl	1	73.13%
apps/emqx_machine/src/emqx_machine.erl	1	77.42%
apps/emqx_management/src/emqx_mgmt_util.erl	1	13.79%
apps/emqx_resource/src/emqx_resource_buffer_worker.erl	1	94.57%
apps/emqx/src/emqx_crl_cache.erl	1	91.21%
apps/emqx/src/emqx_logger.erl	1	80.49%
apps/emqx/src/emqx_schema.erl	1	90.0%
apps/emqx/src/emqx_sys_mon.erl	1	91.67%
apps/emqx/src/emqx_channel.erl	2	87.64%

Totals
Change from base Build 4702850776:	0.1%
Covered Lines:	25611
Relevant Lines:	31488

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💛 - Coveralls

[thalesmg]

Had to rebase to fix conflicts in the i18n files.