In the context of the reference types proposal, the imaginary sub type
of all types was called "bot". With this CL we use this name now also
in V8.

R=clemensh@chromium.org

Bug: v8:9396
Change-Id: I65a2a177ae2af97e66549e7a5b1457595b04a1d8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1675950
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62361}