Test automation for Rancher charts

[kkaempf]

Based on the findings of #4465, write a test automation.

Ensure we have a pipeline in place running those tests

[mmartin24]

Initial Appco automation here: rancher/fleet-e2e#565

We start installing only 3 charts: alertmanager, tika and valkey. More to come soon.

Fleet-468: connects AppCo credentials for fleet-local and fleet-default namespaces.
Fleet-469: installs alertmanager chart via AppCo into local cluster.
Fleet-470: installs tika + valkey charts via AppCo into downstream cluster.

Charts will be increased in following up iterations