MB-70370: Expose {Key,Seq}IndexReadTime and ReadIOAmp Histograms

This patch exposes these newly added histograms to prometheus.

Change-Id: I9392d11d488c8d29f2324421a9cf8f5ce82861d7
Reviewed-on: https://review.couchbase.org/c/kv_engine/+/239398
Tested-by: Build Bot <build@couchbase.com>
Reviewed-by: Jim Walker <jim@couchbase.com>

Author: anirudhRowjee

engines/ep/src/kvstore/magma-kvstore/magma-kvstore.cc

@@ -4002,6 +4002,18 @@ void MagmaKVStore::addTimingStats(const AddStatFn& add_stat,
                       histoStats.FlushTimeHisto,
                       add_stat,
                       c);
+    add_prefixed_stat(prefix,
+                      "keyIndexReadTime",
+                      histoStats.KeyStats.ReadTimeHisto,
+                      add_stat,
+                      c);
+    add_prefixed_stat(prefix,
+                      "seqIndexReadTime",
+                      histoStats.SeqStats.ReadTimeHisto,
+                      add_stat,
+                      c);
+    add_prefixed_stat(
+            prefix, "readIOAmp", histoStats.ReadIOAmpHisto, add_stat, c);
     add_prefixed_stat(
             prefix, "getStatsTime", histoStats.GetStatsTimeHisto, add_stat, c);
     add_prefixed_stat(prefix,