fix: Watchdog Termination is not supported in Synthetics env

[ganeshnj]

What and why?

After starting dogfooding WT, we saw 300+ terminations caused by WT in s8s but those are not actually WT but normal terminations caused by https://github.com/appium/appium-xcuitest-driver/blob/main/lib/real-device.js#L216 API. This API is used by s8s for Restart Application special action.

How?

Add extra syntheticsEnvironment state variable which stores the state if the app was running in s8s or not. This value is determined based on the presence of _dd.synthetics.test_id or _dd.synthetics.result_id env vars.

I couldn't find any other information in the form of env var, args or launch args which we can use to make a decision so it not only covers s8s but also covers other UI automation frameworks.

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference
• Add CHANGELOG entry for user facing changes

Custom CI job configuration (optional)

• Run unit tests for Session Replay