Support for namespace-level configuration of pod tolerations and node selector

Synced from Eclipse Che issue

https://github.com/eclipse/che/issues/20884

Is your task related to a problem? Please describe

As a Eclipse Che admin, I want to be able to set up the configuration of pod tolerations and node selector. Devworkspace operator expected them as k8s namespace annotations:

    metadata: 
      annotations: 
        controller.devfile.io/node-selector: |
          {
            "test-node-selector": "test"
          }
        controller.devfile.io/pod-tolerations: |
          [
            {
              "key": "key1",
              "operator": "Equal",
              "value": "value1",
              "effect": "NoSchedule"
            }
          ]

see more https://github.com/devfile/devworkspace-operator/pull/696

Describe the solution you'd like

Che-operator should grab existing configuration from che-server's env var configuration CHE_WORKSPACE_POD_NODE__SELECTOR and CHE_WORKSPACE_POD_TOLERATIONS__JSON and put them in a format expected by devworkspace operator.

Describe alternatives you've considered

n/a

Release Notes Text

It is now possible to specify pod tolerations and node selector for workspaces of a Che instance setting a CustomCheProperty in CheCluster CR. It's not possible to specify that for just one workspace or for one user: it's a global config.