- Set as uninstallable app
- Update docs
- Adjust specs

Rescue and put into :uninstall_errored if something goes wrong while
destroying, which can happen. I think it is safe to expose the full
error message from the destroy error.

Remove the :uninstalled state as no longer used.

Added :uninstalled state as wasn't sure if we should be destroying the
cluster apps

- Adds to specs the case where apps are also updated
- Rename scope calls on Gitlab::UsageData and Clusters::Cluster
- Removes a duplicated spec

Given https://github.com/helm/helm/issues/3338, I think that we should
exclude applications that are :update_errored, :updating as well.

This could be potentially useful to all cluster applications.

Address followup issue https://gitlab.com/gitlab-org/gitlab-ce/issues/56524

We can have multiple and conditional transistions in a event, so make
use of that.

- #update_errored? method def is redundant, already defined from state
machine
- #update_in_progress? moved to ApplicationStatus
- #ready_status becomes a constant. Previously it was extended in ee/ so
maybe that was why it's a instance method

Before this commit updating Prometheus (e.g. adding alerts) made it
"updated" therefore not installed.

Cluster applications in CE will need access to the same status values
for updating

Partially addresses #47424.