[sil] Eliminate end_borrow_argument now that end_borrow has a single operand.

I changed all of the places that used end_borrow_argument to use end_borrow.

NOTE: I discovered in the process of this patch that we are not verifying
guaranteed block arguments completely. I disabled the tests here that show this
bad behavior and am going to re-enable them with more tests in a separate PR.
This has not been a problem since SILGen does not emit any such arguments as
guaranteed today. But once I do the SILGenPattern work this will change.

rdar://33440767

lib/SIL/SILInstructions.cpp

@@ -790,10 +790,6 @@ StoreBorrowInst::StoreBorrowInst(SILDebugLocation DebugLoc, SILValue Src,
     : InstructionBase(DebugLoc, Dest->getType()),
       Operands(this, Src, Dest) {}
 
-EndBorrowArgumentInst::EndBorrowArgumentInst(SILDebugLocation DebugLoc,
-                                             SILArgument *Arg)
-    : UnaryInstructionBase(DebugLoc, SILValue(Arg)) {}
-
 StringRef swift::getSILAccessKindName(SILAccessKind kind) {
   switch (kind) {
   case SILAccessKind::Init: return "init";