enhancement(observability): Add metrics to measure transform processing time

[bruceg]

Summary

Adds the component_processing_time_seconds histogram and component_processing_time_mean_seconds gauge internal_metrics, exposing the time an event spends in a single transform including the transform buffer.

Vector configuration

How did you test this PR?

Unit tests and watching an internal_metrics => transform => console topology.

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

Notes

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