feat: add XPostCreateTarget interface for post-creation target custom…

[ColdsteelRail]

…ization

Add XPostCreateTarget as an optional interface that XSetController can implement to apply additional modifications to targets after their names are assigned but before they are created on the API server. This enables use cases like setting pod hostname based on the pod name.

The hook is called in both the scale-out and replace creation paths.

1. Does this PR affect any open issues?(Y/N) and add issue references (e.g. "fix #123", "re #123".):

• N
• Y

2. What is the scope of this PR (e.g. component or file name):

3. Provide a description of the PR(e.g. more details, effects, motivations or doc link):

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Other

4. Are there any breaking changes?(Y/N) and describe the breaking changes(e.g. more details, motivations or doc link):

• N
• Y

5. Are there test cases for these changes?(Y/N) select and add more details, references or doc links:

• Unit test
• Integration test
• Benchmark (add benchmark stats below)
• Manual test (add detailed scripts or steps below)
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6. Release note

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