feat: do not allow starting a DevWorkspace if there is already one running

[ibuziuk]

What does this PR do?

Do not allow starting a DevWorkspace if there is already one running

What issues does this PR fix or reference?

eclipse-che/che#21032

Based on the internal discussion, for the time being, it was decided not to add extra property similar to CHE_LIMITS_USER_WORKSPACES_RUN_COUNT since we only support the common PVC strategy, so by definition only a single running workspace is allowed for RWO volumes.

Is it tested? How?

Release Notes

Docs PR

N/A

[openshift-ci]

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This pull-request has been approved by: ibuziuk

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[openshift-ci]

@ibuziuk: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/v8-dashboard-happy-path	b760a08	link	true	/test v8-dashboard-happy-path

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[ibuziuk]

closing in favour of #472