[clang][DebugInfo][test] Convert Objective-C property2.m test to check LLVM IR (llvm#165297)

This patch series renames these Objective-C property tests to something
more descriptive and adjusts them to check IR. Currently the tests check
raw assembly output (not even dwarfdump). Which most likely hid some
bugs around property debug-info.

(cherry picked from commit 5d9df8f)

Author: Michael137

clang/test/DebugInfo/ObjC/property-explicit-ivar.m

@@ -0,0 +1,22 @@
+// RUN: %clang_cc1 -emit-llvm -debug-info-kind=limited %s -o - | FileCheck %s
+
+// CHECK: ![[BASE_PROP:[0-9]+]] = !DIObjCProperty(name: "base"
+// CHECK-SAME:                                    attributes: 2316
+// CHECK-SAME:                                    type: ![[P1_TYPE:[0-9]+]]
+//
+// CHECK: ![[P1_TYPE]] = !DIBasicType(name: "int"
+//
+// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "_customIvar"
+// CHECK-SAME:           extraData: ![[BASE_PROP]]
+
+@interface C {
+  int _customIvar;
+}
+@property int base;
+@end
+
+@implementation C
+@synthesize base = _customIvar;
+@end
+
+void foo(C *cptr) {}