[heap] Separate gc reason strings output in GCTracer.

Change-Id: I6a823ef3b65da2d1010a385db65e368fee9f31e0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3351788Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Hannes Payer <hpayer@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78426}

src/heap/gc-tracer.cc

@@ -564,7 +564,7 @@ void GCTracer::Print() const {
       "[%d:%p] "
       "%8.0f ms: "
       "%s%s%s %.1f (%.1f) -> %.1f (%.1f) MB, "
-      "%.1f / %.1f ms %s (average mu = %.3f, current mu = %.3f) %s %s\n",
+      "%.1f / %.1f ms %s (average mu = %.3f, current mu = %.3f) %s; %s\n",
       base::OS::GetCurrentProcessId(),
       reinterpret_cast<void*>(heap_->isolate()),
       heap_->isolate()->time_millis_since_init(),