Rewrite some isPlusOne calls to isPlusOneOrTrivial.

Whenever we want to forward to a +1 value but don't need to destroy
the original memory, use isPlusOneOrTrivial.

This follows the existing naming scheme.

Fixes rdar://108001491 (SIL verification failed: Found mutating or
consuming use of an in_guaranteed parameter?!:
!ImmutableAddressUseVerifier().isMutatingOrConsuming(fArg))

lib/SILGen/SILGenPattern.cpp

@@ -1679,7 +1679,7 @@ emitCastOperand(SILGenFunction &SGF, SILLocation loc,
     finalValue =
         SGF.emitSubstToOrigValue(loc, finalValue, abstraction, sourceType, ctx);
   }
-  assert(finalValue.isPlusOne(SGF));
+  assert(finalValue.isPlusOneOrTrivial(SGF));
 
   // If we at this point do not require an address, return final value. We know
   // that it is a +1 take always value.