CAMEL-23052: Use type converter for HTTP query header in HttpSendDynamicAware

[gnodet]

Summary

• Fixed HttpSendDynamicAware.createPreProcessor() to use getHeader(key, String.class) instead of casting (String) getHeader(key) for both HTTP_QUERY and HTTP_PATH headers, preventing ClassCastException when header values are non-String types (e.g., Integer).
• Added unit tests verifying that non-String header values (Integer) are properly converted to String via the type converter.

Test plan

• Unit tests added in HttpSendDynamicAwareTest covering Integer-valued HTTP_QUERY, Integer-valued HTTP_PATH, and String-valued HTTP_QUERY headers
• All existing tests in camel-http-base pass

[github-actions]

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