Introduce %_ToNumber intrinsic, which just calls to the existing
ToNumberStub, and remove all uses of our custom JavaScript plus
intrinsics based ToNumber and friends.

Also replace the TO_NUMBER_INLINE macro with TO_NUMBER,
which is currently a wrapper for %_ToNumber. Newly written JS
code should use TO_NUMBER (similar to TO_STRING, TO_INT32,
and friends).

Also finally remove the DefaultString/DefaultNumber builtins, which
are basically the ES5 version of ToPrimitive. Now all code uses the
ES6 version, which is implemented in Object::ToPrimitive and
JSReceiver::ToPrimitive in C++.

CQ_INCLUDE_TRYBOTS=tryserver.v8:v8_linux_layout_dbg,v8_linux_nosnap_dbg
R=jarin@chromium.org
BUG=v8:4307
LOG=n

Review URL: https://codereview.chromium.org/1384443002

Cr-Commit-Position: refs/heads/master@{#31054}