Configure flex deployment to use UserAssignedIdentity

[nturinski]

Fixes #4484
Fixes #4466

It was pretty easy to fix the function triggers not syncing. There was just a couple of things I had to reconfigure in the functionAppConfig and seems like everything is working swell.

Since we are misconfiguring a user's app with no easy way to fix it, I think we should ship this ASAP 🔥

Luckily, I think it didn't totally break them since they could deploy, but I'm sure that it had some other strange trickle effects.

3:47:54 PM naturins-test-flex: Created zip file with artifacts as /home/site/artifacts/a88ee62f-5390-48c6-af81-77325e7d2185.zip.
3:47:54 PM naturins-test-flex: [UploadPackageStep] starting.
3:47:54 PM naturins-test-flex: Using Kudu.Legion.Core.Storage.BlobContainerStorage
3:47:54 PM naturins-test-flex: Created blob name: released-package.zip
3:47:54 PM naturins-test-flex: Created blob uri: https://naturinstestflex.blob.core.windows.net/app-package-naturins-test-flex-88421dd/released-package.zip
3:47:54 PM naturins-test-flex: Token Endpoint: http://169.254.255.2:8081/msi/token?api-version=1.0&resource=https://naturinstestflex.blob.core.windows.net&mi_res_id=/subscriptions/843d979b-47f8-4bb9-9fbc-33e33962c304/resourcegroups/naturinstestflex/providers/Microsoft.ManagedIdentity/userAssignedIdentities/naturinstestflex-identities-2fdd81
3:47:55 PM naturins-test-flex: Received Token using user assigned identity
3:47:55 PM naturins-test-flex: Uploaded blob successfully.
3:47:55 PM naturins-test-flex: Uploaded package to storage blob. Deployment is partially successful from here.
3:47:55 PM naturins-test-flex: [RemoveWorkersStep] starting.
3:47:55 PM naturins-test-flex: RemoveAllWorkers, statusCode = NoContent
3:47:55 PM naturins-test-flex: Reset all workers was successful.
3:47:55 PM naturins-test-flex: [SyncTriggerStep] starting.
3:47:55 PM naturins-test-flex: Waiting 60 seconds for the workers to recycle with deployed content.
3:48:55 PM naturins-test-flex: [CleanUpStep] starting.
3:48:55 PM naturins-test-flex: Cleaned the source packages directory.
3:48:55 PM naturins-test-flex: Cleaned the result artifact directory.
3:48:55 PM naturins-test-flex: Finished deployment pipeline.
3:48:57 PM naturins-test-flex: Querying triggers...
3:49:02 PM naturins-test-flex: HTTP Trigger Urls:
  ResultsFunction: https://naturins-test-flex.azurewebsites.net/api/resultsfunction
  VoteFunction: https://naturins-test-flex.azurewebsites.net/api/votefunction