Fixes implementation of insert_mov_immed_arch to mov encoded value of given instruction, instead of wrongly using the encode estimate. This also fixes instrlist_insert_mov_instr_addr.
Handles INSTR_kind imm16 operands in codec, which are used in mov instrs to store in a reg the encoded addr of an instr.
Adds codec test to verify that the correct bits are stored by the codec, as given by the shift amount and opnd size args. Also adds a drdecode test to verify instrlist_insert_mov_instr_addr.
Fixes: #4609 (closed)