Finished Fifo API to track and retrieve item count from fifo queue

[Arcmantis18]

Hello,

Going through the codebase I noticed that though fifo_pop decremented item_count when popping an item, fifo_push did not increment the item_count for every item stored in the queue. I added this and provided an interface to retrieve the item count from the queue.

This is useful for analytics and benchmarking.

Thank you,

Arcmantis