vmon: set details mode to default off

The "on" default for validator monitor details incurs a heavy
performance penalty on large-validator setups - this may cause excess
memory usage or slowdowns when metrics are queried - this PR changes the
default to off, as was intended for the 23.1.0 release.

Author: arnetheduck

beacon_chain/conf.nim

@@ -560,7 +560,7 @@ type
 
       validatorMonitorDetails* {.
         desc: "Publish detailed metrics for each validator individually - may incur significant overhead with large numbers of validators"
-        defaultValue: true
+        defaultValue: false
         name: "validator-monitor-details" .}: bool
 
       validatorMonitorTotals* {.