If a script was shared between multiple modules (because they used the
same wire bytes) it could happen that we still triggered multiple
"scriptParsed" events via CDP. This was because
{WasmEngine::GetOrCreateScript} did not communicate back whether it
used a cached script or whether it created a new one.

This CL moves the call to {Debug::OnAfterCompile} (which triggers the
"scriptParsed" event) to the {WasmEngine::GetOrCreateScript} method,
such that we only call it once per script.
Since the engine only holds a weak reference to the script, we would
still trigger multiple events if the script is garbage-collected in the
meantime. In this case there is no way around this, as the new script
would have a new ID, hence we need to emit a new event to make it
public to the debugger.

R=thibaudm@chromium.org
CC=bmeurer@chromium.org

Bug: chromium:1151211
Change-Id: I1a7986514fd708680541a0e5dc24e60f01f42c28
Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_isolates_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_rel_ng
Cq-Include-Trybots: luci.v8.try:v8_mac64_gc_stress_dbg_ng
Cq-Include-Trybots: luci.v8.try:v8_linux_gc_stress_dbg_ng
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2687755Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72648}