[synthetic-monitoring-agent] feat: add ability to enable features by environment variable

[tylerauerbeck]

Resolves #3578

Allows user to enable features by environment variable

[Sheikh-Abubaker]

could you please elaborate your use case ?

[tylerauerbeck]

Currently if you deploy the helm chart as is, when you go to run the test check of your synthetic check, it fails with something resembling a timeout error. However, what's actually causing this is that the adhoc feature isn't enabled. This change would allow you to enable the adhoc feature (or any other feature found here) when deploying the chart.