Currently we have V8 RuntimeCallStats that is independently from tracing when
running d8 with flag --runtime_call_stats. This patch embeds V8 runtime call
stats into tracing, by having a global table of runtime call counters each
isolate, resetting the table each time we enter a top level trace event, and
dumping the table for each top level trace event. This will make trace file more
compat, as well as enable runtime call stats in tracing system.

This patch adds ~5% overhead to V8 when the category is enabled, we measure the
overhead by running a script when category is enabled.

BUG=5089

Review-Url: https://codereview.chromium.org/2187693002
Cr-Commit-Position: refs/heads/master@{#38270}