[SandboxIR] Make some instruction constructors private

This patch changes the visibility of the constructors of CatchSwitchInst
ResumeInst and SwitchInst to private instead of public.
This is similar to all other Sandbox IR instructions. The constructor
is private to force the user go through the Context create* API.

The issue was exposed by: llvm#119824

Author: Vasileios Porpodas

llvm/include/llvm/SandboxIR/Instruction.h

@@ -1744,11 +1744,12 @@ class GetElementPtrInst final
 
 class CatchSwitchInst
     : public SingleLLVMInstructionImpl<llvm::CatchSwitchInst> {
-public:
   CatchSwitchInst(llvm::CatchSwitchInst *CSI, Context &Ctx)
       : SingleLLVMInstructionImpl(ClassID::CatchSwitch, Opcode::CatchSwitch,
                                   CSI, Ctx) {}
+  friend class Context; // For accessing the constructor in create*()
 
+public:
   static CatchSwitchInst *create(Value *ParentPad, BasicBlock *UnwindBB,
                                  unsigned NumHandlers, InsertPosition Pos,
                                  Context &Ctx, const Twine &Name = "");
@@ -1833,10 +1834,11 @@ class CatchSwitchInst
 };
 
 class ResumeInst : public SingleLLVMInstructionImpl<llvm::ResumeInst> {
-public:
   ResumeInst(llvm::ResumeInst *CSI, Context &Ctx)
       : SingleLLVMInstructionImpl(ClassID::Resume, Opcode::Resume, CSI, Ctx) {}
+  friend class Context; // For accessing the constructor in create*()
 
+public:
   static ResumeInst *create(Value *Exn, InsertPosition Pos, Context &Ctx);
   Value *getValue() const;
   unsigned getNumSuccessors() const {
@@ -1848,10 +1850,11 @@ class ResumeInst : public SingleLLVMInstructionImpl<llvm::ResumeInst> {
 };
 
 class SwitchInst : public SingleLLVMInstructionImpl<llvm::SwitchInst> {
-public:
   SwitchInst(llvm::SwitchInst *SI, Context &Ctx)
       : SingleLLVMInstructionImpl(ClassID::Switch, Opcode::Switch, SI, Ctx) {}
+  friend class Context; // For accessing the constructor in create*()
 
+public:
   static constexpr const unsigned DefaultPseudoIndex =
       llvm::SwitchInst::DefaultPseudoIndex;