The current tracing (in the "v8.wasm" category) has no indication about
the compilation tiers, which makes it hard to see when baseline
compilation finished and how long top tier compilation takes. The
disabled-by-default "v8.wasm.detailed" category on the other hand is
much too detailed for bigger modules, such that we run into a tracing
buffer overflow pretty quickly, and lose subsequent events.

This CL adds general trace events for baseline compilation and top tier
compilation, which are not per-unit but per-thread. Hence their number
is much lower than the number of events in "v8.wasm.detailed". Because
the events for baseline compilation and top tier compilation have
different colors, it's pretty easy to see whether baseline compilation
or top-tier compilation happens.

R=ahaas@chromium.org

Change-Id: Ic581a335f74018681fa552d14b81c48217b5a80c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2502337Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70832}