[DynInst_API:] [dyninst/dyninst] e38d57: fix x86_64 ret instruction formatting (#1457)

[kupsch <noreply@xxxxxxxxxx>]

  Branch: refs/heads/master
  Home:   https://github.com/dyninst/dyninst
  Commit: e38d57c9904ab623350e90e0e3adcab2afcf2100
      https://github.com/dyninst/dyninst/commit/e38d57c9904ab623350e90e0e3adcab2afcf2100
  Author: kupsch <kupsch@xxxxxxxxxxx>
  Date:   2023-07-25 (Tue, 25 Jul 2023)

  Changed paths:
    M instructionAPI/h/Instruction.h
    M instructionAPI/src/Instruction.C
    M instructionAPI/src/InstructionDecoder-x86.C

  Log Message:
  -----------
  fix x86_64 ret instruction formatting (#1457)

The ret instruction formats incorrectly with an operand of '(%rsp)'.  The
operand should have been flagged as implicit so it is not included in
the output.

- eliminate all but one overloaded Instruction::appendOperand` using
  default parameters

- add isImplicit parameter defaulting to false to
  Instruction::addSuccessor

- add isImplicit to the ret instruction's addSuccessor call to set the
  ret_addr (which adds the operand to the Instruction object)