Port eb5fe0df

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, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1878233002

Cr-Commit-Position: refs/heads/master@{#35424}