Tag Policy: Add unit tests for SDKV2 `CustomizeDiff` interceptor

[jar-b]

Description

Unit tests for the Plugin SDKV2 CustomizeDiff interceptor were not completed in time for the initial release of tag policy support. Test cases should match those from the Plugin Framework ModifyPlan interceptor.

Important Facts and References

Relates #45143

Would you like to implement a relevant change?

No

[github-actions]

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