Update test to ensure that we're actually dealing with existential values

Typed throws took out the existential boxing for us, causing this
test to fail. Add more explicit boxing back in so that we still test
elimination of it.

Author: DougGregor

test/SILOptimizer/existential_box_elimination.swift

@@ -23,7 +23,7 @@ public struct TestError: Error {
 
 @inline(never)
 @_optimize(none)
-internal func internalImplementation(somethingGood: Bool) -> Result<Int, TestError> {
+internal func internalImplementation(somethingGood: Bool) -> Result<Int, any Error> {
   return somethingGood ? .success(27) : .failure(TestError(errno:123))
 }
 
@@ -32,12 +32,11 @@ public func publicWrapper(somethingGood: Bool) throws -> Int {
 }
 
 // CHECK-LABEL: sil [noinline] @$s4test0A13WithForceCast13somethingGoodSiSb_tF
-// CHECK:       [[F:%[0-9]+]] = function_ref @$s4test22internalImplementation13somethingGoods6ResultOySiAA9TestErrorVGSb_tF
+// CHECK:       [[F:%[0-9]+]] = function_ref @$s4test22internalImplementation13somethingGoods6ResultOySis5Error_pGSb_tF
 // CHECK:       apply [[F]]
 // CHECK:       switch_enum
 // CHECK:     bb1:
 // CHECK-NOT:   alloc_existential_box
-// CHECK-NOT:   apply
 // CHECK: } // end sil function '$s4test0A13WithForceCast13somethingGoodSiSb_tF'
 @inline(never)
 public func testWithForceCast(somethingGood: Bool) -> Int {
@@ -49,12 +48,11 @@ public func testWithForceCast(somethingGood: Bool) -> Int {
 }
 
 // CHECK-LABEL: sil [noinline] @$s4test0A19WithMultipleCatches13somethingGoodSiSb_tF
-// CHECK:       [[F:%[0-9]+]] = function_ref @$s4test22internalImplementation13somethingGoods6ResultOySiAA9TestErrorVGSb_tF
+// CHECK:       [[F:%[0-9]+]] = function_ref @$s4test22internalImplementation13somethingGoods6ResultOySis5Error_pGSb_tF
 // CHECK:       apply [[F]]
 // CHECK:       switch_enum
 // CHECK:     bb1:
 // CHECK-NOT:   alloc_existential_box
-// CHECK-NOT:   apply
 // CHECK: } // end sil function '$s4test0A19WithMultipleCatches13somethingGoodSiSb_tF'
 @inline(never)
 public func testWithMultipleCatches(somethingGood: Bool) -> Int {