C++ IR: Make TOperand cached

Just like `TInstruction` is cached to prevent re-numbering its tuples in
every IR query, I think `TOperand` should be cached too. I tested it on
the small comdb2 snapshot, where it only saves one second of work when
running a second IR query, but the savings should grow when snapshots
are larger and when there are more IR queries in a suite. Tuple
numbering is mildly quadratic, so it should be good to avoid repeating
it.

Adding these annotations adds three cached stages to the existing four
cached stages of the IR. The new cached stages are small and do not
appear to repeat any work from the other stages, so I see no advantage
to merging them with the existing stages.

Author: jbj

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Operand.qll

@@ -6,6 +6,7 @@ import semmle.code.cpp.ir.implementation.MemoryAccessKind
 import semmle.code.cpp.ir.internal.Overlap
 private import semmle.code.cpp.ir.internal.OperandTag
 
+cached
 private newtype TOperand =
   TRegisterOperand(Instruction useInstr, RegisterOperandTag tag, Instruction defInstr) {
     defInstr = Construction::getRegisterOperandDefinition(useInstr, tag)

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Operand.qll

@@ -6,6 +6,7 @@ import semmle.code.cpp.ir.implementation.MemoryAccessKind
 import semmle.code.cpp.ir.internal.Overlap
 private import semmle.code.cpp.ir.internal.OperandTag
 
+cached
 private newtype TOperand =
   TRegisterOperand(Instruction useInstr, RegisterOperandTag tag, Instruction defInstr) {
     defInstr = Construction::getRegisterOperandDefinition(useInstr, tag)

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/Operand.qll

@@ -6,6 +6,7 @@ import semmle.code.cpp.ir.implementation.MemoryAccessKind
 import semmle.code.cpp.ir.internal.Overlap
 private import semmle.code.cpp.ir.internal.OperandTag
 
+cached
 private newtype TOperand =
   TRegisterOperand(Instruction useInstr, RegisterOperandTag tag, Instruction defInstr) {
     defInstr = Construction::getRegisterOperandDefinition(useInstr, tag)