Revert of PPC: [compiler] Drop the CompareNilIC. (patchset #1 id:1 of https://codereview.chromium.org/1733663003/ )

Reason for revert:
Original commit reverted.

Original issue's description:
> PPC: [compiler] Drop the CompareNilIC.
>
> Port 666aec03
>
> Original commit message:
>     Since both null and undefined are also marked as undetectable now, we
>     can just test that bit instead of having the CompareNilIC try to collect
>     feedback to speed up the general case (without the undetectable bit
>     being used).
>
>     Drive-by-fix: Update the type system to match the new handling of
>     undetectable in the runtime.
>
> R=bmeurer@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com
> BUG=
>
> Committed: https://crrev.com/546ea6b8393a894f07597ade5ec1c7db02c1e425
> Cr-Commit-Position: refs/heads/master@{#34266}

TBR=bmeurer@chromium.org,joransiu@ca.ibm.com,jyan@ca.ibm.com,michael_dawson@ca.ibm.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=

Review URL: https://codereview.chromium.org/1736253003

Cr-Commit-Position: refs/heads/master@{#34340}