Merge EE Cypress tests with the OSS ones (#15887)

* Merge all enterprise specs together with the OSS ones

* Move whitelabel under `/admin/settings`

* Move specs under `/admin/audit` folder

* Merge `admin/database/add` specs

* Group snippets

* Merge OSS and EE sso specs

* Move sandboxes under `admin/permissions`

* Delete custom drill-throughs spec

* Return boolean value

* Use `Cypress.env` instead of global vars

* Delete empty spec

* Update paths for `eslint` script