Reland "[vm/ffi] Remove deprecated Struct.addressOf getter"

This got deprecated in Dart 2.12 stable. Removing for the next release.

Closes: #40667

This reverts commit 1d1f68f.

Change-Id: I1df84f2225ea68c2d8ccb7d3e6359050e8802f62
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/188291
Reviewed-by: Zach Anderson <zra@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>

sdk/lib/ffi/struct.dart

@@ -58,10 +58,3 @@ abstract class Struct extends NativeType {
 
   Struct._fromPointer(this._addressOf);
 }
-
-/// Extension on [Struct] specialized for its subtypes.
-extension StructAddressOf<T extends Struct> on T {
-  /// Returns the address backing the reference.
-  @Deprecated('Hold on to the pointer backing a struct instead.')
-  Pointer<T> get addressOf => _addressOf as Pointer<T>;
-}

tests/ffi/structs_nnbd_workaround_test.dart

@@ -98,8 +98,6 @@ void testTypeTest() {
   final pointer = calloc<Coordinate>();
   Coordinate c = pointer.ref;
   Expect.isTrue(c is Struct);
-  // TODO(https://dartbug.com/40667): Remove support for this.
-  Expect.isTrue(c.addressOf is Pointer<Coordinate>);
   calloc.free(pointer);
 }
 

tests/ffi/structs_test.dart

@@ -128,8 +128,6 @@ void testTypeTest() {
   final pointer = calloc<Coordinate>();
   Coordinate c = pointer.ref;
   Expect.isTrue(c is Struct);
-  // TODO(https://dartbug.com/40667): Remove support for this.
-  Expect.isTrue(c.addressOf is Pointer<Coordinate>);
   calloc.free(pointer);
 }
 

tests/ffi_2/structs_test.dart

@@ -128,8 +128,6 @@ void testTypeTest() {
   final pointer = calloc<Coordinate>();
   Coordinate c = pointer.ref;
   Expect.isTrue(c is Struct);
-  // TODO(https://dartbug.com/40667): Remove support for this.
-  Expect.isTrue(c.addressOf is Pointer<Coordinate>);
   calloc.free(pointer);
 }