feat(opentelemetry sink): add use_otlp_encoding option

[pront]

Summary

The main purpose of this feature is to simplify OTEL sink configuration from:

otel_sink:
  inputs:
    - otel.logs
  type: opentelemetry
  protocol:
    type: http
    uri: http://localhost:5318/v1/logs
    method: post
  encoding:
     codec: protobuf
     protobuf:
       desc_file: path/to/opentelemetry-proto.desc
       message_type: opentelemetry.proto.collector.logs.v1.ExportLogsServiceRequest
    framing:
      method: "bytes"
    request:
      headers:
      content-type: "application/x-protobuf"

to

otel_sink:
  inputs:
    - source0.logs
  type: opentelemetry
  use_otlp_encoding: true
  protocol:
    type: http
    uri: http://otel-collector-sink:5318/v1/logs
    method: post
    batch:
      max_events: 1
    request:
      headers:
        content-type: application/json

I had to implement default for EncodingConfigWithFraming otherwise users would have to set a codec that would always be ignored. Hence the numerous CUE changes.

Vector configuration

How did you test this PR?

E2E tests were adapted.

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

Related: #23524

Notes

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[pront]

/ci-run-e2e-opentelemetry-logs