Investigate on-demand live test secret helper

ARM deployment output values are available to anyone with read access to the subscription, so for example if a service dumps out some connection strings for a static resource, anyone with subscription read access can go look those up. If we can get all the languages using a common test env lookup helper, then we can transition to a solution that doesn't use ARM deployment outputs for common or service-specific secrets and rather have secrets go into something more on-demand like a keyvault.

No files, tests, or entry points are named. Start by tracing how ARM deployment outputs currently expose test secrets across languages and documenting the existing helper patterns; done means a concrete investigation result for a common on-demand lookup approach and its effect on service-specific secrets.

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