Add FXIOS-14220 [perftest] Emit perfherder JSON artifact

[junngo]

📜 Tickets

Jira ticket
Github issue

💡 Description

Firefox-ios performance tests currently only output PERFHERDER_DATA to the log.
This PR adds support for generating a perfherder-data JSON artifact (perfherder-data.json) to enable correct ingestion in Treeherder and downstream tooling.

📝 Checklist

• I filled in the ticket numbers and a description of my work
• I updated the PR name to follow our PR naming guidelines
• I ensured unit tests pass and wrote tests for new code
• If working on UI, I checked and implemented accessibility (Dynamic Text and VoiceOver)
• If adding telemetry, I read the data stewardship requirements and will request a data review
• If adding or modifying strings, I read the guidelines and will request a string review from l10n
• If needed, I updated documentation and added comments to complex code

[junngo]

Hi @isabelrios :)
I submitted a PR to solve the issue. From what I can see, jobs for firefox-ios only appear in Treeherder once the code has landed on main. Is there a way to trigger this perftest[0] job (or something equivalent) directly so that I can verify the perfherder JSON artifact before landing?

[0] example
https://treeherder.mozilla.org/jobs?repo=firefox-ios&fromchange=dab2846f826e986dd7b831534ff8f89eb75c6f82&selectedTaskRun=RMftNDvrQReJC56ppTDJUg.0