Since {NativeModule::GetCode} returns a raw pointer to {WasmCode}, it
needs to increment the reference counter on that code object.
{HasCode} on the other hand does not return a code pointer, so it's
implemented separately now.

R=mstarzinger@chromium.org

Bug: v8:8217
Change-Id: I812981aaf89281fb0296682114f248079e57a5e3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1566514Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60843}