Change the base command for flow export from AzmgmtCommand to PowerPlatformCommand.

Here we can change all https://api.bap.microsoft.com resource occurrences to this.resource. Also vice-versa, changing the current this.resource to https://management.azure.com/.

Initial request: #3397 (comment)