Update TraitCodegenWriter

[hpmellema]

Background

Updates the trait codegen writer to:

1. Use a static factory class
2. Add a CapitalizingFormatter formatter for $U
3. Normalize symbol references before adding to duplicate map to avoid false positive duplicates (for example Map<String, String> and Map<String, Integer> would currently be marked as duplicates because their references differ, causing the Map class to use a fully qualified name unnecessarily)
4. Put resolved placeholder values directly into context map rather than instantiating a second hashmap.

Testing

• Ran existing integration and unit tests

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