[safepoint] Avoid unconditional store after std::{min,max}

Instead of cmov + unconditional store, do a conditional store. At least
on Intel CPUs, this turns out to be significantly faster.

R=jkummerow@chromium.org

Bug: v8:13063
Change-Id: Ib5a89b9b9dbc88ca408a4bafc152d91407bf8d1b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3776675Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81900}

src/codegen/safepoint-table.h

@@ -238,9 +238,9 @@ class SafepointTableBuilder : public SafepointTableBuilderBase {
 
   void UpdateMinMaxStackIndex(int index) {
 #ifdef DEBUG
-    max_stack_index_ = std::max(max_stack_index_, index);
+    if (index > max_stack_index_) max_stack_index_ = index;
 #endif  // DEBUG
-    min_stack_index_ = std::min(min_stack_index_, index);
+    if (index < min_stack_index_) min_stack_index_ = index;
   }
 
   int min_stack_index() const {