PPC: Mark null and undefined as undetectable, and use it to handle abstract equality comparison in the generic compare ic

Port 3ce9e808

Original commit message:
    Marking as undetectable makes abstract equality of null, undefined, and
    other undetectable objects easier. Supporting it in the generic compare
    IC significantly speeds up dynamic comparison between those values and
    JSReceivers by not falling back to the runtime.

R=verwaest@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1684133003

Cr-Commit-Position: refs/heads/master@{#33876}