SPIRE-380 : Add e2e tests for CreateOnlyMode, UpgradeableCondition, and LabelPropagation (#91)

* Add e2e tests for CreateOnlyMode, UpgradeableCondition, and LabelPropagation

This PR adds comprehensive e2e test coverage for three features:

## CreateOnlyMode Tests (PContext - Pending)
Tests for CREATE_ONLY_MODE environment variable handling:
- Baseline (no env var set)
- CREATE_ONLY_MODE=true/false (lowercase)
- CREATE_ONLY_MODE=TRUE/FALSE (uppercase, case-insensitive)
- Invalid and empty string values
- Env var removal transition

**Note:** These tests are marked as PContext (pending/skipped) due to an
operator bug where the CreateOnlyMode condition does not transition from
True to False when the CREATE_ONLY_MODE env var is set to 'false' or removed.
The condition remains stuck at True. Tests will be enabled once the operator
bug is fixes available in the build

## UpgradeableCondition Tests
Tests for OLM Upgradeable condition management:
- Upgradeable=True when all operands are ready
- Upgradeable=False when pods are deleted (SpireServer, SpireAgent, OIDC)
- Recovery to Upgradeable=True after pod restoration
- Multiple concurrent pod failures handling
- Operator restart recovery
- Condition field verification (type, status, reason, message)

## LabelPropagation Tests
Tests for spec.labels propagation to workload metadata:
- SpireServer → StatefulSet metadata.labels
- SpireAgent → DaemonSet metadata.labels
- SpiffeCSIDriver → DaemonSet metadata.labels
- SpireOIDCDiscoveryProvider → Deployment metadata.labels
- Label removal verification (clearing spec.labels)

## Utils Refactoring
- Simplified containsAny() using strings.Contains
- Extracted common verifyWorkloadLabel() helper to reduce duplication
- Added WaitForDaemonSetLabelAbsent() helper for label removal tests
- Added condition helpers: GetConditionByType, WaitForConditionStatus,
  WaitForConditionAbsent
- Added OperatorCondition helpers for Upgradeable condition checks
- Added label verification helpers for StatefulSet, DaemonSet, Deployment

## New Constants
- CreateOnlyMode condition constants
- UpgradeableCondition constants
- Label propagation test constants

* update the revome subcription config

* Incorporate review comments

Signed-off-by: Yuedong Wu <dwcn22@outlook.com>

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Signed-off-by: Yuedong Wu <dwcn22@outlook.com>
Co-authored-by: Super User <root@sayadas-thinkpadp16vgen1.bengluru.csb>
Co-authored-by: SAYAK DAS <sayadas@sayadas-thinkpadp16vgen1.bengluru.csb>
Co-authored-by: Yuedong Wu <dwcn22@outlook.com>

Author: 4 people