Provide powershell runtime version override for Logic Apps apps

[jviau]

Logic Apps needs a way for their customers to override powershell runtime versions. Currently powershell uses FUNCTIONS_WORKER_RUNTIME_VERSION which is a general app setting. Since logic apps is a multi-language environment, we want to give them a more specific app setting and keep this change scoped to only logic apps.

Plan

When the app is a logic app, and when we are resolving powershell worker.config.json, we will:

1. Replace FUNCTIONS_WORKER_RUNTIME_VERSION with LOGIC_APPS_POWERSHELL_VERSION, if available
2. Expand environment variables in worker.config.json
3. Restore original value of FUNCTIONS_WORKER_RUNTIME_VERSION