[rram_ctrl,dv] Track wr_fifo/rd_fifo occupancy in rram_ctrl scoreboard

on_mem_access() is an empty stub; needs real FIFO-occupancy tracking cross-checked against fifo_lvl/curr_fifo_lvl.

Locate the rram_ctrl scoreboard and its empty on_mem_access() stub, then trace how wr_fifo, rd_fifo, fifo_lvl, and curr_fifo_lvl are represented. Implement occupancy tracking for both FIFOs and cross-check the tracked values against the reported levels. Run the relevant rram_ctrl verification tests to confirm the scoreboard detects mismatches.

Written by the indexing model from the issue text.