Refactor type casting in Cython files for improved clarity and consistency

- Updated various Cython files to explicitly cast types, enhancing type safety and readability.
- Adjusted the `engine_name` property in `InferenceEngine` and its subclasses to be set directly in the constructor.
- Modified the `request` method in `_SessionWithBase` to accept `*args` for better flexibility.
- Ensured proper type casting for return values in methods across multiple classes, including `Inference`, `CoreMLEngine`, and `TensorRTEngine`.

These changes aim to streamline the codebase and improve maintainability by enforcing consistent type usage.

annotation.pyx

@@ -3,7 +3,7 @@ cimport constants_inf
 
 cdef class Detection:
     def __init__(self, double x, double y, double w, double h, int cls, double confidence):
-        self.annotation_name = None
+        self.annotation_name = ""
         self.x = x
         self.y = y
         self.w = w
@@ -54,7 +54,7 @@ cdef class Annotation:
         return f"{self.name}: {detections_str}"
 
     cdef bytes serialize(self):
-        return msgpack.packb({
+        return <bytes>msgpack.packb({
             "n": self.name,
             "mn": self.original_media_name,
             "i": self.image,  # "i" = image