Create pipeline for executing storage ui tests on demand

[asnaith]

Goal: Configure a custom github actions workflow that executes the current Storage UI test suite on the dev branch / staging api.

Details: Configuration should be almost the same as a current job used for testing PRs except with a different trigger point. We already have something in place for files so we can reference that configuration.

Purpose: To aid the API team when they are making changes to staging API. The team has their own tests but for extra confidence in their changes, they would like to be able to execute the UI test suite to ensure the frontend also responds well. We are currently running the Files test suite when they notify us of changes to stage but we should be also running our storage tests too.

Acceptance criteria:

• Workflow can be run on demand, tests get executed
• Test results are sent to the "imploy-ui-notif" slack channel

Notes: Not all API endpoints are covered by the frontend test suite.