Include the NSKeyValueObserving extension for NSObject (#1329)

Fixes #1327

Author: liamappelbe

pkgs/ffigen/lib/src/code_generator/objc_built_in_functions.dart

@@ -54,11 +54,13 @@ class ObjCBuiltInFunctions {
     'NSMutableData',
     'NSMutableDictionary',
     'NSMutableIndexSet',
+    'NSMutableOrderedSet',
     'NSMutableSet',
     'NSMutableString',
     'NSNotification',
     'NSNumber',
     'NSObject',
+    'NSOrderedSet',
     'NSProxy',
     'NSSet',
     'NSString',
@@ -83,6 +85,9 @@ class ObjCBuiltInFunctions {
     'NSEnumerationOptions',
     'NSItemProviderFileOptions',
     'NSItemProviderRepresentationVisibility',
+    'NSKeyValueChange',
+    'NSKeyValueObservingOptions',
+    'NSKeyValueSetMutationKind',
     'NSOrderedCollectionDifferenceCalculationOptions',
     'NSSortOptions',
     'NSStringCompareOptions',

pkgs/objective_c/ffigen_objc.yaml

@@ -32,11 +32,13 @@ objc-interfaces:
     - NSMutableData
     - NSMutableDictionary
     - NSMutableIndexSet
+    - NSMutableOrderedSet
     - NSMutableSet
     - NSMutableString
     - NSNotification
     - NSNumber
     - NSObject
+    - NSOrderedSet
     - NSProxy
     - NSSet
     - NSString
@@ -63,6 +65,9 @@ enums:
     - NSEnumerationOptions
     - NSItemProviderFileOptions
     - NSItemProviderRepresentationVisibility
+    - NSKeyValueChange
+    - NSKeyValueObservingOptions
+    - NSKeyValueSetMutationKind
     - NSOrderedCollectionDifferenceCalculationOptions
     - NSSortOptions
     - NSStringCompareOptions

pkgs/objective_c/lib/objective_c.dart

@@ -43,18 +43,23 @@ export 'src/objective_c_bindings_generated.dart'
         NSItemProvider,
         NSItemProviderFileOptions,
         NSItemProviderRepresentationVisibility,
+        NSKeyValueChange,
+        NSKeyValueObservingOptions,
+        NSKeyValueSetMutationKind,
         NSLocale,
         NSMethodSignature,
         NSMutableArray,
         NSMutableData,
         NSMutableDictionary,
         NSMutableIndexSet,
+        NSMutableOrderedSet,
         NSMutableSet,
         NSMutableString,
         NSNotification,
         NSNumber,
         NSObject,
         NSOrderedCollectionDifferenceCalculationOptions,
+        NSOrderedSet,
         NSProxy,
         NSRange,
         NSSet,