[NFC] Move llvm.fptrunc.round to Floating-Point Conversion Intrinsics class (#155854)
Floating-Point Conversion Intrinsics - is a new category of intrinsics,
that do not fall into other categories and can be used for conversions
with explicit rounding modes and mini-floats conversions.
Signed-off-by: Sidorov, Dmitry <dmitry.sidorov@intel.com>