Add stats for scan and eviction profiling

Add duration histogram stats to profile total scan duration:

1. "throttle_hist_reader"
2. "tryEvictPages_clock_hist_reader"
3. "tryEvictPages_evict_hist_reader"
4. "itr_sek_hist_reader"
5. "itr_seek_hist_reader"

Throttle duration stats:

1. "avg_throttle_dur_reader"
2. "avg_throttle_dur_writer"
3. "avg_throttle_dur_other"

Eviction rate stats:

1. "burst_eviction_rate"
2. "periodic_eviction_rate"
3. "eviction_rate_reader"
4. "eviction_rate_writer"
5. "eviction_rate_swapper"
6. "eviction_rate_other"