This reland is after fix in [heap] Delete wrong DCHECK.
It includes moving ProxyGetProperty to its own stub to reduce
binary size.

This is a reland of 47a97aa5
Original change's description:
> [builtins] Port getting property from Proxy to CSA
> 
> Bug: v8:6559, v8:6557
> Change-Id: If6c51f5483adb73ddd2495cede5d85e887a3c298
> Reviewed-on: https://chromium-review.googlesource.com/589212
> Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
> Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
> Commit-Queue: Maya Lekova <mslekova@google.com>
> Cr-Commit-Position: refs/heads/master@{#47113}

Bug: v8:6559, v8:6557
Change-Id: I76acd97ba1acb62b7e7983db1741441d997050f0
Reviewed-on: https://chromium-review.googlesource.com/600215
Commit-Queue: Maya Lekova <mslekova@google.com>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Franziska Hinkelmann <franzih@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47159}