If a tracing session starts after a script load has happened, then it is
not emitted, so the source information is not visible in ETW. This is
because we keep track of the loads already emitted, and we try to launch
traces even when recording is not happening.

To prevent this problem, this CS keeps track of when recording is
happening. So, when it starts, it will emit all the already generated
code immediately. This will add some overhead on tracing session start
if system instrumentation is enabled, but this is better than not
having instrumentation for previous symbols.

There is still one problem: for each active isolate, it calls for
replaying the event recording in an asynchronous task. So, for any
JS task that is already running when tracing start, symbols will not
be available. This makes this change less useful as, for a batch task
or any long JS code that is already running when tracing start, we
will not get symbols yet. Only after the foreground task runner runs
the task to emit the ETW events we will get the symbols resolved in
the trace.

An specific approach was required for d8 interactive shell. As, when
showing prompt, it is not processing the task runner queue, and it
is only processed when the next script is launched, it first checks
if it needs to generate ETW symbols information before running the
script.

Bug: v8:12932
Change-Id: I8b056c69cee0350f921a01c87beb9f2d51e10583
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3705541Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: José Dapena Paz <jdapena@igalia.com>
Cr-Commit-Position: refs/heads/main@{#81673}