Fix tests to reflect new eager bridging semantics

* Some tests were removed because they exclusively check for lazy bridge
  behaviour
* Many checks for objc/native-ness were removed as meaningless
* Many checks for identity were updated (or removed) for new semantics
* Trap checks were updated to reflect more eager semantics
* A keysEnumerator() impl had to be added as the new design touches it
* Some tests that randomly touch impl details were updated

Author: Alexis Beingessner

test/stdlib/Inputs/DictionaryKeyValueTypesObjC.swift

@@ -18,21 +18,6 @@ public func convertNSDictionaryToDictionary<
   return result!
 }
 
-func isNativeDictionary<KeyTy : Hashable, ValueTy>(
-  _ d: Dictionary<KeyTy, ValueTy>) -> Bool {
-  switch d._variantBuffer {
-  case .native:
-    return true
-  case .cocoa:
-    return false
-  }
-}
-
-func isCocoaDictionary<KeyTy : Hashable, ValueTy>(
-  _ d: Dictionary<KeyTy, ValueTy>) -> Bool {
-  return !isNativeDictionary(d)
-}
-
 func isNativeNSDictionary(_ d: NSDictionary) -> Bool {
   let className: NSString = NSStringFromClass(type(of: d)) as NSString
   return ["_SwiftDeferredNSDictionary", "NativeDictionaryStorage"].contains {

test/stdlib/RuntimeObjC.swift

@@ -425,17 +425,6 @@ Runtime.test("casting AnyObject to class metatypes") {
 
 var RuntimeFoundationWrappers = TestSuite("RuntimeFoundationWrappers")
 
-RuntimeFoundationWrappers.test("_stdlib_NSObject_isEqual/NoLeak") {
-  nsObjectCanaryCount = 0
-  autoreleasepool {
-    let a = NSObjectCanary()
-    let b = NSObjectCanary()
-    expectEqual(2, nsObjectCanaryCount)
-    _stdlib_NSObject_isEqual(a, b)
-  }
-  expectEqual(0, nsObjectCanaryCount)
-}
-
 var nsStringCanaryCount = 0
 @objc class NSStringCanary : NSString {
   override init() {

test/stdlib/SetTrapsObjC.swift

@@ -134,13 +134,8 @@ SetTraps.test("Downcast1")
     reason: "this trap is not guaranteed to happen in -Ounchecked"))
   .code {
   let s: Set<NSObject> = [ NSObject(), NSObject() ]
-  let s2: Set<TestObjCKeyTy> = _setDownCast(s)
   expectCrashLater()
-  let v1 = s2.contains(TestObjCKeyTy(10))
-  let v2 = s2.contains(TestObjCKeyTy(20))
-
-  // This triggers failure.
-  for m in s2 { }
+  _ = _setDownCast(s) as Set<TestObjCKeyTy>
 }
 
 SetTraps.test("Downcast2")