We currently take the sample at the moment the isolate is created. At
that point, the embedder callback for taking samples is not installed
yet. Hence delay taking the sample until the first module is created.
This will only take samples for isolates that actually use wasm, which
will reduce the overall number of samples, but will give a better
picture of PKU support for Wasm.

R=jkummerow@chromium.org
CC=dlehmann@google.com

Bug: v8:11714
Change-Id: I8a4163961c06076efd6c5dde5751682b53863c2c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2944429Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74975}