[RISCV] Improve RISCVOperand Printing (llvm#126179)

We've gradually added more information to the RISCVOperand structure,
but the debug output has never caught up, which is quite confusing. This
adds printing for many of additional the fields in the structure, where
they are relevant.

In addition to this, we now have quite a lot of internal registers which
share names with each other - e.g. X0_H, X0_W, X0, X0_Pair all have the
same name - so also print the enum value to differentiate these.

llvm/lib/Target/RISCV/AsmParser/RISCVAsmParser.cpp

@@ -1116,18 +1116,21 @@ struct RISCVOperand final : public MCParsedAsmOperand {
 
     switch (Kind) {
     case KindTy::Immediate:
-      OS << *getImm();
+      OS << "<imm: " << *Imm.Val << " " << (Imm.IsRV64 ? "rv64" : "rv32")
+         << ">";
       break;
     case KindTy::FPImmediate:
+      OS << "<fpimm: " << FPImm.Val << ">";
       break;
     case KindTy::Register:
-      OS << "<register " << RegName(getReg()) << ">";
+      OS << "<reg: " << RegName(Reg.RegNum) << " (" << Reg.RegNum
+         << (Reg.IsGPRAsFPR ? ") GPRasFPR>" : ")>");
       break;
     case KindTy::Token:
       OS << "'" << getToken() << "'";
       break;
     case KindTy::SystemRegister:
-      OS << "<sysreg: " << getSysReg() << '>';
+      OS << "<sysreg: " << getSysReg() << " (" << SysReg.Encoding << ")>";
       break;
     case KindTy::VType:
       OS << "<vtype: ";