[INSTA-47091] fix: Improved getting active tracer and current span mechanism

[CagriYonca]

tracing_is_off function is also widely used in almost every instrumentation and it only returns whether the tracer is ready to record a new span or not. As I already explained above, we already have this information in the tracer, so that by combining these two functions into get_tracer_tuple function, we're getting rid of 1 get_current_span call and functionality of tracing_is_off function since we can directly check if the tracer in the instrumentation is False or not.

• get_active_tracer and tracing_is_off functions has been removed
• adapted instrumentations to the new get_tracer_tuple function