Add Helm Tests for Thanos

Write necessary cypress and script tests to ensure that CI will accurately be able to tell that Thanos is running healthy and as we would expect.

Here is an overview and the required templates for implementing these tests for a bigbang package via gluon: https://repo1.dso.mil/big-bang/apps/library-charts/gluon/-/blob/master/docs/bb-tests.md

AC:

• Write cypress tests to check the Thanos UI for successful login.