Stop including af-enums.h in Darwin unit tests.

These are Objective-C files, and should not be including potentially-C++
headers.

A bunch of "test that the code is 0" checks were replaced with "error is nil"
checks (and some were removed, if "error is nil" was already being tested).

The macro definition reformatting in MTRBackwardsCompatTests.m is just from
updates to our clang-format version, looks like.

Author: bzbarsky-apple

src/darwin/Framework/CHIPTests/MTRBackwardsCompatTests.m

@@ -23,8 +23,6 @@
 #import "MTRTestResetCommissioneeHelper.h"
 #import "MTRTestStorage.h"
 
-#import <app/util/af-enums.h>
-
 #import <math.h> // For INFINITY
 
 // system dependencies
@@ -203,34 +201,34 @@ - (void)test000_SetUp
     // tests.
 }
 
-#define CHECK_RETURN_TYPE(sig, type)                                                                                               \
-    do {                                                                                                                           \
-        XCTAssertNotNil(sig);                                                                                                      \
-        XCTAssertTrue(strcmp([sig methodReturnType], @encode(type)) == 0);                                                         \
+#define CHECK_RETURN_TYPE(sig, type)                                       \
+    do {                                                                   \
+        XCTAssertNotNil(sig);                                              \
+        XCTAssertTrue(strcmp([sig methodReturnType], @encode(type)) == 0); \
     } while (0)
 
 /**
  * Arguments 0 and 1 are the implicit self and _cmd arguments; the real arguments begin at index 2.
  */
-#define CHECK_ARGUMENT(sig, index, type)                                                                                           \
-    do {                                                                                                                           \
-        XCTAssertTrue(strcmp([sig getArgumentTypeAtIndex:(index) + 2], @encode(type)) == 0);                                       \
+#define CHECK_ARGUMENT(sig, index, type)                                                     \
+    do {                                                                                     \
+        XCTAssertTrue(strcmp([sig getArgumentTypeAtIndex:(index) + 2], @encode(type)) == 0); \
     } while (0)
 
-#define CHECK_READONLY_PROPERTY(instance, propName, type)                                                                          \
-    do {                                                                                                                           \
-        NSMethodSignature * signature = [instance methodSignatureForSelector:@selector(propName)];                                 \
-        CHECK_RETURN_TYPE(signature, type);                                                                                        \
-        /* Check that getting the property directly compiles too */                                                                \
-        (void) instance.propName;                                                                                                  \
+#define CHECK_READONLY_PROPERTY(instance, propName, type)                                          \
+    do {                                                                                           \
+        NSMethodSignature * signature = [instance methodSignatureForSelector:@selector(propName)]; \
+        CHECK_RETURN_TYPE(signature, type);                                                        \
+        /* Check that getting the property directly compiles too */                                \
+        (void) instance.propName;                                                                  \
     } while (0)
 
-#define CHECK_PROPERTY(instance, propName, setterName, type)                                                                       \
-    do {                                                                                                                           \
-        CHECK_READONLY_PROPERTY(instance, propName, type);                                                                         \
-        NSMethodSignature * signature = [instance methodSignatureForSelector:@selector(setterName:)];                              \
-        CHECK_RETURN_TYPE(signature, void);                                                                                        \
-        CHECK_ARGUMENT(signature, 0, type);                                                                                        \
+#define CHECK_PROPERTY(instance, propName, setterName, type)                                          \
+    do {                                                                                              \
+        CHECK_READONLY_PROPERTY(instance, propName, type);                                            \
+        NSMethodSignature * signature = [instance methodSignatureForSelector:@selector(setterName:)]; \
+        CHECK_RETURN_TYPE(signature, void);                                                           \
+        CHECK_ARGUMENT(signature, 0, type);                                                           \
     } while (0)
 
 /**