Switch-interpreter: Use more helpers for opcode arguments.

Second half of the rename. The old VReg methods returned a variety
of integer type (sign/size) so this CL isn't necessarily trivial.

Test: diff libart.so disassembly between PS1 and PS2
Change-Id: Ic41492e4e86e950b8cc2fb9c0b5ef68b97763811
1 file changed