This CL adds support for builtins with JavaScript linkage written using
the TurboFan CodeStubAssembler, but with a JSCall descriptor (which was
already supported thanks to a previous patch by Ben Smith). As a first
example, we convert the Math.sqrt builtin and thereby get rid of the
%_MathSqrt intrinsic, which causes trouble for the representation
selection pass in the JavaScript pipeline.

R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/1824993002

Cr-Commit-Position: refs/heads/master@{#34989}