Consolidate sandboxing reproduction tests (#13943)

* Extract signIn function

* Extract `USER_GROUPS`

* Extract `user_id` attribute in a constant

* Extract permission updating into a helper function

* Refactor and unskip repro for metabase-enterprise#535 (#13944)

https://github.com/metabase/metabase-enterprise/issues/535

* Apply new helper function to `sandboxes.cy`

* #13641 Repro: Drill-through on implicit join tables withsandboxes (#13953) [ci skip]

* Add TODO comments for future improvements [ci noskip]

* Add `cy.log` to trigger the proper CI run