[wasm] Fix write-protection performance for lazy asm.js

Similar to https://crrev.com/c/2912786, this fixes a high number of
page permission switches (incuring mprotect syscall and lock contention
overhead) by pulling a {NativeModuleModificationScope} outside of a
loop (and across a function boundary).

R=clemensb@chromium.org
CC=​​​jkummerow@chromium.org

Cq-Include-Trybots: luci.v8.try:v8_linux64_fyi_rel_ng
Bug: v8:11663, chromium:932033
Change-Id: I2ec47f3eeeb2ab9624d2eaea9b4e776738871c97
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2928504


Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Daniel Lehmann <dlehmann@google.com>
Cr-Commit-Position: refs/heads/master@{#74906}