Added the ability to see project deployments using a group cluster

Only display the details of the cluster page when the cluster
exists. If it is in "creating" state, show a message and a spinner

Use update term instead of update in the clusters managed app
implementation in order to make the implementation and UI
language more consistent.

The new component also implements several improvements in the
knative domain editor workflow:

- Display a loading spinner when saving changes in the domain name
- Display success toast message indicating changes were saved
successfully.
- Display error message in the contraty occurs

Added a changelog entry for the feature

- Vue confirmation modal implementation
- CSS tweaks for modal default height

- Separate cluster application UI state from server-side app status
- Use a state machine to determine cluster application next state
- Instead of using two variables to keep track of when an app
is installing or updating, just use the app status property and control
server-side and user events using the FSM service.

Implemented the toast component for success messages

Move cluster applications manager tests from karma to jest. Fixes
some migration issues related with timeouts, and HTTP request
expectations.

if there isn’t an ingress IP assigned for the cluster yet

When ingress application is installed, the cluster domain help text
is updated to indicate that ingress external ip can be used as the
cluster domain

Uses a new factory method to DRY instantiation.

Added the functionality to edit the Knative domain

This reverts merge request !24485

https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8731

This reverts commit 427c1e72, reversing
changes made to 5aac64a7.

Show a dismissable callout on a users dashboard for a free trial of
the GitLab.com Gold plan. Hide the callout from users who have
dismissed the callout, are already on a trial or are already on the
gold plan

This reverts merge request !21551