We had some (dead) logic to create different parameter values pending on
the position of the parameter. As it was not used any more, it got
removed in https://crrev.com/c/3003464.
This CL changes the existing logic for creating default parameter values
to use a similar logic, which matches what --wasm-fuzzer-gen-test
creates and has a slightly higher chance of triggering interesting
behaviour.

R=ahaas@chromium.org

Change-Id: Ibb4394c1978f25d70166a03002e084211bfe7e1e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3003465
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75619}