[CoroutineAccessors] Don't observe caller errors.

Experience with `_modify`/`_read` has shown that it is never desireable
to cleanup differently based on whether the caller has thrown.  Emit an
`end_apply` in either case.

Author: nate-chandler

lib/SILGen/SILGenApply.cpp

@@ -4989,7 +4989,11 @@ class EndCoroutineApply : public Cleanup {
       SGF.B.createEndBorrow(l, *i);
       SGF.B.createDestroyValue(l, (*i)->getOperand());
     }
-    if (forUnwind) {
+    auto *beginApply =
+        cast<BeginApplyInst>(ApplyToken->getDefiningInstruction());
+    auto isCalleeAllocated = beginApply->isCalleeAllocated();
+    auto unwindOnCallerError = !isCalleeAllocated;
+    if (forUnwind && unwindOnCallerError) {
       SGF.B.createAbortApply(l, ApplyToken);
     } else {
       SGF.B.createEndApply(l, ApplyToken,

test/SILGen/coroutine_accessors.swift

@@ -115,7 +115,7 @@ public var irm: Int {
 // CHECK:      dealloc_stack [[OLD_VALUE_ADDR]]
 // CHECK:      return [[OLD_VALUE]]
 // CHECK:    bb2([[ERROR:%[^,]+]] : @owned $any Error):
-// CHECK:      abort_apply [[TOKEN]]
+// CHECK:      end_apply [[TOKEN]]
 // CHECK:      end_access [[SELF_ACCESS]]
 // CHECK:      dealloc_stack [[NEW_VALUE_ADDR]]
 // CHECK:      dealloc_stack [[OLD_VALUE_ADDR]]