feat(codecs): introduce OTLP decoder

[pront]

Summary

• Introduces otlp decoder.
• Uses it for the opentelemetry source

Implemented with flexibility in mind (iterative approach).
Follow-up PR will improve performance before we release this feature.

Vector configuration

For manual tests I used the following config:

api:
  enabled: true

sources:
  source0:
    type: opentelemetry
    grpc:
      address: 0.0.0.0:4317
    http:
      address: 0.0.0.0:4318
    use_otlp_decoding: true
sinks:
  console:
    type: console
    inputs:
      - source0.logs
      - source0.metrics
      - source0.traces
    encoding:
      codec: json
      pretty: true

How did you test this PR?

Unit tests and also used by existing OTEL E2E tests.

Manually with:

telemetrygen traces \
  --otlp-endpoint=localhost:4318 \
  --otlp-http \
  --otlp-insecure \
  --traces 1 \
  --service="telemetrygen-test"

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: #23975

Notes

• Please read our Vector contributor resources.
• Do not hesitate to use @vectordotdev/vector to reach out to us regarding this PR.
• Some CI checks run only after we manually approve them.
  • We recommend adding a pre-push hook, please see this template.
  • Alternatively, we recommend running the following locally before pushing to the remote branch:
    • make fmt
    • make check-clippy (if there are failures it's possible some of them can be fixed with make clippy-fix)
    • make test
• After a review is requested, please avoid force pushes to help us review incrementally.
  • Feel free to push as many commits as you want. They will be squashed into one before merging.
  • For example, you can run git merge origin master and git push.
• 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.

[thomasqueirozb]

As discussed offline OtlpDeserializer could use some improvements to not blindly try all 3 deserializers but the current implementation should work just fine. It's a nice user facing improvement