Added unit test for cmd/resourcedistributiongenerator/generator/targets.go

[GautamBytes]

What's in this PR?

This PR significantly improves the quality and reliability of the ResourceDistribution generator by introducing two comprehensive test suites and fixing a critical bug that was uncovered during the process.

The Bug Fix in targets.go

The most important change is a fix to the newNameListRNode function in targets.go.

Problem: The function was generating an invalid YAML structure for namespace lists that would be rejected by the Kubernetes API server.

# Incorrect (Old) Output
includedNamespaces:
  list:
  - name: ns1
  - name: ns2

Solution: The function has been corrected to produce a simple list of strings, which is the valid schema required by the ResourceDistribution CRD.

# Correct (New) Output
includedNamespaces:
  list:
  - ns1
  - ns2

New Test Coverage
Two new test files have been added to validate the generator's behavior:

resourcedistribution_test.go: A high-level test for the main MakeResourceDistribution function.
targets_test.go: A granular unit test for the complex validation and transformation logic in targets.go.

These tests cover all key scenarios, including:
Data generation via literalSources.
Applying options to resources via resourceOptions.
Combining all targeting mechanisms (allNamespaces, included/excluded lists, label selectors).
All error and validation paths.

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[GautamBytes]

@furykerry please take a look!