[llvm] Reapply "[MC][TableGen] Expand Opcode field of MCInstrDesc" (#180321) (PR #180954)

[Erich Keane via llvm-commits]

erichkeane wrote:

I'm seeing this build error with Clang18 as my compiler, is it from this patch? 

```
/local/home/ekeane/llvm-project/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp:1476:22: error: call to 'getTargetMemOpcode' is ambiguous
 1476 |   if (NumOps == 3 && SystemZ::getTargetMemOpcode(MemOpcode) != -1) {
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~
/local/home/ekeane/llvm-project/llvm/lib/Target/SystemZ/SystemZInstrInfo.h:163:9: note: candidate function
  163 | int64_t getTargetMemOpcode(uint32_t Opcode);
      |         ^
/local/home/ekeane/llvm-project/build/lib/Target/SystemZ/SystemZGenInstrInfo.inc:15689:5: note: candidate function
 15689 | int getTargetMemOpcode(uint16_t Opcode) {
       |     ^
1 error generated.
```

https://github.com/llvm/llvm-project/pull/180954