Adds RuntimeStats counters for HeapBrokerInitialization, Serialize,
SerializeMetadata and Finalization phases. These happen only on main thread.
In a followup cl we will also add counters for other phases that could happen
on main thread or background thread.

Earlier RecompileSynchronous was used to measure the time spent in Concurrent,
non Concurrent and Concurrent finalize phases. This cl replaces them with
OptimizeConcurrent, OptimizeNonConcurrent and OptimizeConcurrentFinalize
counters. This cl also renames RecompileConcurrent to OptimizeBackground to
make it clear this measures the background component of optimization.

This also updates names of trace events to be in-sync with RuntimeStat counters.

Bug: v8:9684
Change-Id: Ifda81ce7ab1c659c2df53bab924c51c46f46939b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1924439Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Dan Elphick <delphick@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Mythri Alle <mythria@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65147}