Rate limit transaction counters (#5447)

* Rate limit transaction counters

* @sakridge feedback

* Set default high metrics rate for multinode demo

* Fix tests

* Swap defaults and fix env var tests

* Only set metrics rate if not already set

multinode-demo/common.sh

@@ -60,6 +60,10 @@ solana_replicator=$(solana_program replicator)
 
 export RUST_BACKTRACE=1
 
+if [[ -z $SOLANA_METRICS_HIGH_RATE ]]; then
+  export SOLANA_METRICS_HIGH_RATE=1000
+fi
+
 # shellcheck source=scripts/configure-metrics.sh
 source "$SOLANA_ROOT"/scripts/configure-metrics.sh