Move quantization to new backend (#10363)

* Move quantization logic to GGML via new backend

This moves the model aware logic to Go code and calls GGMLs quantization code for model creation.

* Remove "add model quantizations"

This is no longer needed now that quantization is implemented in Go+GGML code directly.

server/model.go

@@ -64,7 +64,7 @@ func parseFromModel(ctx context.Context, name model.Name, fn func(api.ProgressRe
 			}
 			defer blob.Close()
 
-			f, _, err := ggml.Decode(blob, 1024)
+			f, _, err := ggml.Decode(blob, -1)
 			if err != nil {
 				return nil, err
 			}