feat: add OpenAI image generation endpoint support

This commit introduces comprehensive support for OpenAI's image generation API endpoint (/v1/images/generations).

Changes include:
- New OpenAI image generation schema definitions with full API support
- Image generation processor for handling requests and responses
- Translator implementation for OpenAI-to-OpenAI image generation
- Comprehensive test coverage for the new functionality
- Support for DALL-E models and image generation parameters

The implementation follows the existing patterns in the codebase and provides
full compatibility with OpenAI's Images API specification.

Signed-off-by: Hrushikesh Patil <[email protected]>

Author: nutanix-Hrushikesh

.gitignore

@@ -49,4 +49,3 @@ inference-extension-conformance-test-report.yaml
 .mcp.json
 
 .goose
-/aigw