perf_hooks: reset prev_ before starting ELD timer

reset `ELDHistogram.prev_` before staring timer to ensure that start
timer doesn't leak across `disable()` `enable()` calls.

PR-URL: #26693
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>

src/node_perf.cc

@@ -539,6 +539,7 @@ bool ELDHistogram::RecordDelta() {
 bool ELDHistogram::Enable() {
   if (enabled_) return false;
   enabled_ = true;
+  prev_ = 0;
   uv_timer_start(timer_,
                  ELDHistogramDelayInterval,
                  resolution_,