feat: add metrics and tracing support for image generation

This commit extends the observability infrastructure to support image generation operations.

Changes include:
- New image generation metrics implementation with OpenTelemetry integration
- Image generation span and tracer implementations for distributed tracing
- OpenInference schema support for image generation operations
- Updated tracing API to include image generation tracer interface
- Enhanced metrics constants to support image generation operations

The implementation provides comprehensive observability for image generation
requests including latency, success rates, and detailed tracing information
following OpenInference standards.

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

Author: nutanix-Hrushikesh

internal/tracing/api/api.go

@@ -67,11 +67,6 @@ func (NoopTracing) ImageGenerationTracer() ImageGenerationTracer {
 	return NoopImageGenerationTracer{}
 }
 
-// EmbeddingsTracer implements Tracing.EmbeddingsTracer.
-func (NoopTracing) EmbeddingsTracer() EmbeddingsTracer {
-	return NoopEmbeddingsTracer{}
-}
-
 // Shutdown implements Tracing.Shutdown.
 func (NoopTracing) Shutdown(context.Context) error {
 	return nil
@@ -204,35 +199,6 @@ type ImageGenerationSpan interface {
 	EndSpan()
 }
 
-// EmbeddingsTracer creates spans for OpenAI embeddings requests.
-type EmbeddingsTracer interface {
-	// StartSpanAndInjectHeaders starts a span and injects trace context into
-	// the header mutation.
-	//
-	// Parameters:
-	//   - ctx: might include a parent span context.
-	//   - headers: Incoming HTTP headers used to extract parent trace context.
-	//   - headerMutation: The new Embeddings Span will have its context
-	//     written to these headers unless NoopTracing is used.
-	//   - req: The OpenAI embeddings request. Used to record request attributes.
-	//   - body: contains the original raw request body as a byte slice.
-	//
-	// Returns nil unless the span is sampled.
-	StartSpanAndInjectHeaders(ctx context.Context, headers map[string]string, headerMutation *extprocv3.HeaderMutation, req *openai.EmbeddingRequest, body []byte) EmbeddingsSpan
-}
-
-// EmbeddingsSpan represents an OpenAI embeddings request.
-type EmbeddingsSpan interface {
-	// RecordResponse records the response attributes to the span.
-	RecordResponse(resp *openai.EmbeddingResponse)
-
-	// EndSpanOnError finalizes and ends the span with an error status.
-	EndSpanOnError(statusCode int, body []byte)
-
-	// EndSpan finalizes and ends the span.
-	EndSpan()
-}
-
 // ImageGenerationRecorder records attributes to a span according to a semantic
 // convention.
 type ImageGenerationRecorder interface {