Add nebari upgrade tests

[Adam-D-Lewis]

Context

Currently we have no automated deployment tests around running Nebari upgrade. Such a test would have prevented the data loss described in the context of #2700. This is also beneficial more broadly to help catch any error which occurs during the Nebari upgrade process, but not during an initial deployment. These tests should be added.

I propose the tests should upgrade from the last release of Nebari to the latest develop branch. You then check if files, conda envs, and users persisted across the upgrade.

We already have https://github.com/nebari-dev/nebari/blob/develop/.github/workflows/test_local_integration.yaml, https://github.com/nebari-dev/nebari/blob/develop/.github/workflows/test_aws_integration.yaml, https://github.com/nebari-dev/nebari/blob/develop/.github/workflows/test_azure_integration.yaml, https://github.com/nebari-dev/nebari/blob/develop/.github/workflows/test_gcp_integration.yaml as well as the deployment tests. These could be used as references when adding a nebari upgrade test.