This CL moves the remaining runtime DataView getters to Torque,
namely DataViewGetBigInt64/BigUint64, and removes the associated
runtime code that is now unneeded.

All of the DataView getters are now implemented in Torque, which brings
a nice performance improvement over the former C++ builtin code.

Change-Id: I35cf2eabce3c79cc0d3200e7f24dbe0c3e5c2804
Reviewed-on: https://chromium-review.googlesource.com/1092736
Commit-Queue: Théotime Grohens <theotime@google.com>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53765}