[BARX-1009] Use the ddot-collector image by default for the operator

[AliDatadog]

What does this PR do?

Changes the logic for the image selection of the otel-agent container.

Image Selection Matrix

Scenario	UseStandaloneImage	Image Override	OTel Agent Container	Other Containers
Default	true	None	gcr.io/datadoghq/ddot-collector:7.67.0	gcr.io/datadoghq/agent:7.67.0
Override + Supported	true	datadog/agent:7.68.0	datadog/ddot-collector:7.68.0	datadog/agent:7.68.0
Override + Custom Registry	true	custom.io/agent:1.0	custom.io/ddot-collector:1.0	custom.io/agent:1.0
Full Image (no override)	false	None	gcr.io/datadoghq/agent:7.67.0-full	gcr.io/datadoghq/agent:7.67.0-full
Full Image + Override	false	datadog/agent:7.66.0 /!\ broken	datadog/agent:7.66.0 (unchanged)	datadog/agent:7.66.0 (unchanged)

• When UseStandaloneImage is true (default):
  • OTel Agent: respect the registry + tag override, not image name
  • Other containers: respect the entire override
• When UseStandaloneImage is false:
  • If there's an explicit override: respect it entirely
  • If there's no override: apply the -full suffix

Motivation

ddot-collector is the recommended way to deploy the Agent.

Additional Notes

Anything else we should know when reviewing?

With image overrides, the user is responsible for setting the right flavor

Minimum Agent Versions

Are there minimum versions of the Datadog Agent and/or Cluster Agent required?

• Agent: v7.67.0

Describe your test plan

Write there any instructions and details you may have to test your PR.

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

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 84.72222% with 11 lines in your changes missing coverage. Please review.

Project coverage is 47.13%. Comparing base (5dff879) to head (78a8a7c).

Files with missing lines	Patch %	Lines
...ller/datadogagent/feature/otelcollector/feature.go	91.93%	4 Missing and 1 partial ⚠️
...controller/datadogagent/component/agent/default.go	0.00%	3 Missing ⚠️
pkg/images/images.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2012      +/-   ##
==========================================
+ Coverage   47.00%   47.13%   +0.13%     
==========================================
  Files         255      255              
  Lines       25302    25356      +54     
==========================================
+ Hits        11892    11951      +59     
+ Misses      12794    12790       -4     
+ Partials      616      615       -1     

Flag	Coverage Δ
unittests	47.13% <84.72%> (+0.13%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
pkg/testutils/builder.go	93.00% <100.00%> (+0.03%)	⬆️
...controller/datadogagent/component/agent/default.go	87.24% <0.00%> (+0.12%)	⬆️
pkg/images/images.go	96.36% <0.00%> (-1.79%)	⬇️
...ller/datadogagent/feature/otelcollector/feature.go	89.18% <91.93%> (+5.77%)	⬆️

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[truthbk]

Looks good to me (given my operator limitations, take with some🧂) :)

[estherk15]

Left formatting suggestions for consistency.

[tbavelier]

Discussed offline, overrides are reconciled after features, so image changes inside a feature are removed if user is specifying a nodeAgent image.name or image.tag. Logs should be kept, but ManageNodeAgent should be simplified accordingly

[levan-m]

Suggested change

	expectedAgentImage: "gcr.io/datadoghq/agent:7.68.0-full",
	expectedAgentImage: "gcr.io/datadoghq/agent:7.68.0",

[levan-m]

This seems redundant. This change will be built with default version of 7.67 or later, agentVersion will be earlier than 7.67 iff version from image override is earlier than 7.67. In such case we set useStandaloneImage = false.
Then we go through these conditionals where version retrieved from Override leads to no-op block

	if apiutils.BoolValue(o.useStandaloneImage) {
	} else {
		if o.nodeAgentImageOverride != nil {
			// [no-op] User has provided an explicit image override, respect it as-is
		} else {
			// No explicit override, apply the -full suffix logic
                         // only reachable when `useStandaloneImage` is set to false in DDA. 
                }

This can be simplified and cleaned up.