azdev test should warn users if they have configured defaults

Some commands default to values specified by the configured default in the user's environment (set via `az configure`). See `--resource-group` and `--locations` as examples of optionals which support configured defaults.

This can lead to inconsistencies where a test succeeds locally, but fails in the https://github.com/Azure/azure-cli repo's CI.

`azdev test` should warn users that they have configured defaults set which can lead to inconsistent playback behavior of the generated test recordings.