Use conversion helpers in V8Binding.cpp for [Clamp] method arguments

There was custom generated code specifically for handling arguments with
[Clamp], which is quite unnecessary since the toUInt*() have an integer
conversion configuration parameter that among other things can be used to
request clamping.

Related: Fix the somewhat broken handling the |Clamp| integer conversion
configuration in the toUInt*() helpers. An optimization code path for the
case that the V8 value is an int32 forgot to do clamping, there was no
clamping at all in toUInt64(), and +/- Infinity was converted to zero
instead of being clamped.

Clamping support is not added to toInt64(), since the clampTo<> helper in
Source/wtf/MathExtras.h explicitly doesn't support |long long int|, which
is int64_t on some platforms.

BUG=413257

Review URL: https://codereview.chromium.org/563793002

git-svn-id: svn://svn.chromium.org/blink/trunk@181882 bbb929c8-8fbe-4397-9dbb-9b2b20218538