fix: benchmark panic issue resolved.

[Jyothish-POC]

Change Summary

Running cargo bench -p benchmarks --bench exporter from otap-dataflow directory panics on the first iteration:

What issue does this PR close?

• Closes [benchmarks/exporter] benchmark panic #1278

How are these changes tested?

While running cargo bench -p benchmarks --bench exporter now I am getting the below result.

Are there any user-facing changes?

Changelog

• Added a .chloggen/*.yaml entry
• This PR is a chore (indicated in title)
• This is a documentation-only PR.

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[opentelemetry-pr-dashboard]

Pull request dashboard status

Status last refreshed: 2026-07-23 05:26:11 UTC.

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[Jyothish-POC]

Trying to develop the enhancement idea thats mentioned on the issue.

Optional follow-up:

create_otap_batch produces a single-row batch, so the bench's row_size knob loses meaning. A small enhancement (also welcome from a new contributor) is to add create_otap_batch_with_rows(batch_id, payload_type, num_rows) next to create_otap_batch in otap_mock.rs and have the bench vary num_rows so each message carries varying payload weight.