feat: configure securityContext for che-gateway container

[tolusha]

What does this PR do?

feat: configure securityContext for che-gateway container

What issues does this PR fix or reference?

eclipse-che/che#22747

Is it tested? How?

1. Configure CheCluster

spec:
  devEnvironments:
    security:
      containerSecurityContext:
        <...>

2. Start a workspace
3. Check security context in the gateway container

PR Checklist

• E2E tests pass (when PR is ready, comment /test v8-devworkspace-operator-e2e, v8-che-happy-path to trigger)
  • v8-devworkspace-operator-e2e: DevWorkspace e2e test
  • v8-che-happy-path: Happy path for verification integration with Che

[openshift-ci]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: tolusha
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