Enable JIT Kubernetes resource creation for project level clusters

See merge request gitlab-org/gitlab-ce!29515

Since Kubernetes is creating the Secret and token asynchronously it is
necessary that we implement some delay or retrying logic to avoid a race
condition where we fetch a Secret before the token is even set. There
does not appear to be any way for us to force it to be set with any
synchronous API call so retrying seems to be the only option.

Previously this behaviour was only available to group
and instance-level clusters, as some project clusters
relied on Kubernetes credentials being passed through
to the runner instead of having their resources managed
by GitLab (which is not available when using JIT). These
clusters have been migrated to unmanaged, so resources
can be created on demand for the remaining managed clusters.

Immediate configuration is not ideal for group and instance
level clusters as projects that may never be deployed would
still have Kubernetes namespaces and service accounts created
for them.

As of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/25586
we now create only the resources that are required for the
project being deployed, at the time of deployment.

Instance level clusters were already mostly supported, this change adds
admin area controllers for cluster CRUD

When this option is enabled, GitLab will create namespaces and service
accounts as usual. When disabled, GitLab wont create any project
specific kubernetes resources

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/56557