[CONTP-1504] Create DatadogCSIDriver from DDA when createDatadogCSIDriver=true

[tbavelier]

What does this PR do?

When spec.global.csi.enabled=true and the new spec.global.csi.createDatadogCSIDriver=true field is set, the DatadogAgent controller automatically creates a DatadogCSIDriver custom resource owned by the DDA.

This gives users a single-CR experience: configure CSI on their DatadogAgent and the operator handles creating the DatadogCSIDriver. The DatadogCSIDriver controller then reconciles it (DaemonSet, CSIDriver object, etc.).

Key behaviors:

• createDatadogCSIDriver defaults to false — no behavior change for existing users
• The DatadogCSIDriver is treated as a desired-state object (like DDAI): external modifications are reconciled back
• If the DatadogCSIDriver CRD is not installed and the field is not set, nothing happens (safe for clusters without the CRD)
• If the CRD is not installed but the field is set, an error is returned
• Cleanup: toggling the field off deletes the operator-owned DatadogCSIDriver; manually-created ones are left alone
• Only works in the V3 reconcile path (DatadogAgentInternalEnabled=true)

Motivation

Simplify the user experience for CSI driver setup. Instead of requiring users to create both a DatadogAgent and a separate DatadogCSIDriver, they can opt into automatic creation from their DDA spec.

Additional Notes

• The created DatadogCSIDriver currently has an empty spec (the DatadogCSIDriver controller applies its own defaults). A follow-up PR will construct the spec based on relevant DDA fields.
• The DatadogCSIDriver lifecycle is managed via direct API calls (create/update/delete) rather than the dependency store, because the store only supports built-in Kubernetes types. This is documented in code comments.
• Requires the DatadogCSIDriver CRD to be installed and the controller to be enabled (--datadogCSIDriverEnabled).

Minimum Agent Versions

N/A — this is an operator-level feature.

Describe your test plan

Unit tests in ddcsi_test.go cover:

• CSI disabled — no resource created
• CSI enabled + createDatadogCSIDriver=true — resource created with owner reference
• CRD not available — error returned
• createDatadogCSIDriver=false — no resource created
• Idempotency — second reconcile is a no-op
• Spec drift — external modifications reconciled back to desired state
• Cleanup on disable — owned resource deleted
• Cleanup skips unowned — manually-created resources left alone
• Cleanup when CRD absent — no error

Checklist

• PR has at least one valid label: bug, enhancement, refactoring, documentation, tooling, and/or dependencies
• PR has a milestone or the qa/skip-qa label
• All commits are signed (see: signing commits)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 71.92982% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 40.12%. Comparing base (189f12c) to head (932c38e).

Files with missing lines	Patch %	Lines
internal/controller/datadogagent/ddcsi.go	74.54%	7 Missing and 7 partials ⚠️
internal/controller/datadogagent/dependencies.go	0.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2857      +/-   ##
==========================================
+ Coverage   40.06%   40.12%   +0.06%     
==========================================
  Files         319      320       +1     
  Lines       28039    28096      +57     
==========================================
+ Hits        11233    11274      +41     
- Misses      15983    15991       +8     
- Partials      823      831       +8     

Flag	Coverage Δ
unittests	40.12% <71.92%> (+0.06%)	⬆️

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Files with missing lines	Coverage Δ
internal/controller/datadogagent/dependencies.go	60.86% <0.00%> (-2.77%)	⬇️
internal/controller/datadogagent/ddcsi.go	74.54% <74.54%> (ø)

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