[Cypress] Implement adding custom registries and S3 for Rancher UI tests

[thehejik]

In the past Firefox rancher-ui tests were using scenario https://github.com/epinio/epinio-end-to-end-tests/blob/main/cypress/integration/scenarios/with_s3_and_external_registry.spec.ts which refer to installation by using external registries and storage, but I think this couldn't work.

We should implement testing by using a custom registries and s3 storage when installing over Rancher in browser over appropriate text fields in Epinio App dialog.

Problem is that epinioInstall function should be able to handle external_registries and s3 but installation.spec.ts and its epinioInstall call is sending false as an argument for both values, see https://github.com/epinio/epinio-end-to-end-tests/blob/main/cypress/integration/unit_tests/installation.spec.ts#L22