This fixes an issue with ful-codegen where code target entries for the OSR
check were being incorrectly shared. We now explicitly disable sharing of code
target constant pool entries for full-codegen and for calls to builtins from
WASM code, using a scope.

BUG=chromium:725743

Review-Url: https://codereview.chromium.org/2922433002
Cr-Commit-Position: refs/heads/master@{#45661}