Port fa3cbf60

Original Commit Message:

    This changes Torque's builtin pointers to use a Smi representation
    underneath instead of storing the Code target object. Callsites look
    up the target entry point through IsolateData::builtin_entry_table.

    The notable effect of this CL is that builtin pointer calls no longer
    call any on-heap Code.

R=jgruber@chromium.org, joransiu@ca.ibm.com, michael_dawson@ca.ibm.com
BUG=
LOG=N

Change-Id: I49bb08de916fd93e576936a56b0e1a0e21072289
Reviewed-on: https://chromium-review.googlesource.com/c/1394301Reviewed-by: Joran Siu <joransiu@ca.ibm.com>
Commit-Queue: Junliang Yan <jyan@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#58530}