[MIR] Add missing noteNewVirtualRegister callbacks (#111634)

The delegates' callback isn't invoked on parsing new virtual registers.

There are two places in the serialization where new virtual registers can be discovered: in register infos and in instructions.

Author: optimisan

llvm/lib/CodeGen/MIRParser/MIParser.cpp

@@ -1786,6 +1786,7 @@ bool MIParser::parseRegisterOperand(MachineOperand &Dest,
 
         MRI.setRegClassOrRegBank(Reg, static_cast<RegisterBank *>(nullptr));
         MRI.setType(Reg, Ty);
+        MRI.noteNewVirtualRegister(Reg);
       }
     }
   } else if (consumeIfPresent(MIToken::lparen)) {

llvm/lib/CodeGen/MIRParser/MIRParser.cpp

@@ -705,6 +705,7 @@ bool MIRParserImpl::parseRegisterInfo(PerFunctionMIParsingState &PFS,
                          FlagStringValue.Value + "'");
       Info.Flags.push_back(FlagValue);
     }
+    RegInfo.noteNewVirtualRegister(Info.VReg);
   }
 
   // Parse the liveins.