This is mostly a simple copy & paste of the stub implementation from
code-stubs-arch.cc to builtins-arch.cc.

The conversion allows removal of a special case for the DoubleToIStub
within the compiler & wasm pipelines, and also makes the following
builtins isolate-independent (in conjunction with
https://crrev.com/c/1006581):

TFC BitwiseAnd
TFC BitwiseOr
TFC BitwiseXor
TFC Exponentiate
TFC ShiftLeft
TFC ShiftRight
TFC ShiftRightLogical
TFJ AtomicsAdd
TFJ AtomicsAnd
TFJ AtomicsCompareExchange
TFJ AtomicsExchange
TFJ AtomicsLoad
TFJ AtomicsOr
TFJ AtomicsStore
TFJ AtomicsSub
TFJ AtomicsXor
TFJ MathClz32
TFJ MathImul
TFJ MathPow
TFJ NumberParseInt
TFJ StringFromCharCode
TFJ TypedArrayFrom
TFJ TypedArrayOf
TFJ TypedArrayPrototypeMap

Drive-by: dead code removal & TODOs in code-stubs.h.

Bug: v8:6666
Change-Id: I763cba2242bcadc2d130b0aaa16a9787212b466a
Reviewed-on: https://chromium-review.googlesource.com/1012024
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52591}