port 52148c41

Original Commit Message:
    Add relocatable pointers for wasm memory references that need to be updated when wasm GrowMemory is used. Code generator changes to accept relocatable constants as immediates.

R=gdeepti@google.com, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com, bjaideep@ca.ibm.com, mbrandy@us.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1884573003

Cr-Commit-Position: refs/heads/master@{#35426}