feat(codecs): add 'use_json_names' options to protobuf codecs

[pront]

Summary

• Added use_json_names option to protobuf serializer and deserializer to support JSON field naming (camelCase vs snake_case)
• Adopted VRL's Makefile-based approach for generating protobuf test fixtures (deleted custom Python script)

Vector configuration

How did you test this PR?

New test and manually tested with the following config:

api:
  enabled: true
  address: "127.0.0.1:8686"

sources:
  s0:
    type: "opentelemetry"
    grpc:
      address: 0.0.0.0:4317
    http:
      address: 0.0.0.0:4318
      headers: []
    use_otlp_decoding: true

sinks:
  otel_output:
    type: opentelemetry
    inputs:
      - "s0.logs"
    protocol:
      type: http
      uri: http://127.0.0.1:5319/v1/logs
      method: post
      encoding:
        codec: "protobuf"
        protobuf:
          desc_file: /Users/pavlos.rontidis/CLionProjects/vector/pront/otel/proto/opentelemetry-proto.desc
          message_type: "opentelemetry.proto.collector.logs.v1.ExportLogsServiceRequest"
          use_json_names: true
      request:
        headers:
          content-type: application/x-protobuf
      framing:
        method: bytes

  logs_sink:
    type: console
    inputs:
      - s0.logs
    encoding:
      codec: json

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the no-changelog label to this PR.

References

closes: #23971

Notes

• Please read our Vector contributor resources.
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    • make fmt
    • make check-clippy (if there are failures it's possible some of them can be fixed with make clippy-fix)
    • make test
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• If this PR introduces changes Vector dependencies (modifies Cargo.lock), please
  run make build-licenses to regenerate the license inventory and commit the changes (if any). More details here.

[rtrieu]

my feedback is primarily the following:

• update "will look" to "looks" (present tense)
• change "e.g." to "for example" (avoid Latin abbreviations)

can you apply these changes throughout the PR? the first rule is to adhere to our style guide, and the second rule is for translation purposes.

thanks!

[pront]

my feedback is primarily the following:

• update "will look" to "looks" (present tense)
• change "e.g." to "for example" (avoid Latin abbreviations)

can you apply these changes throughout the PR? the first rule is to adhere to our style guide, and the second rule is for translation purposes.

thanks!

Updated rustdocs and regenerated the CUE files