Embedded CLI Subscription fix

[vilit1]

Customer has pointed out that dt create with --subscription does not work. Upon inspection, it was determined that the group show command used to get location of the resource group was not passing in the user defined subscription.

This adds an optional user_subscription to the EmbeddedCLI class. If it is defined, then it will be used during invoke commands. However, a subscription passed into the invoke takes priority over the user_subscription (specifically for the endpoint commands).

This pr ensures all EmbeddedCLI's in non-test code use the user_subscription if defined.

Added a unit test to ensure embeddedcli functions as expected.

pipeline run for dt + adu: https://dev.azure.com/azureiotdevxp/aziotcli/_build/results?buildId=6566&view=results

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[vilit1]

https://dev.azure.com/azureiotdevxp/aziotcli/_build/results?buildId=6573&view=results

[c-ryan-k]

Let's get a history update and a version bump in here and we should be good 👍