feat($resource): add proper support for cancelling requests

Introduced changes:

- Deprecate passing a promise as `timeout` (for `$resource` actions).
  It never worked correctly anyway.
  Now a warning is logged (using `$log.debug()`) and the property is
  removed.
- Add support for a boolean `cancellable` property in actions'
  configuration, the `$resource` factory's `options` parameter and the
  `$resourceProvider`'s `defaults` property.
  If true, the `$cancelRequest` method (added to all returned values for
  non-instance calls) will abort the request (if it's not already
  completed or aborted).
  If there is a numeric `timeout` specified on the action's configuration,
  the value of `cancellable` will be ignored.

Example usage:

```js
var Post = $resource('/posts/:id', {id: '@id'}, {
  get: {
    method: 'GET',
    cancellable: true
  }
});

var currentPost = Post.get({id: 1});
...
// A moment later the user selects another post, so
// we don't need the previous request any more
currentPost.$cancelRequest();
currentPost = Post.get({id: 2});
...
```

BREAKING CHANGE:

Using a promise as `timeout` is no longer supported and will log a
warning. It never worked the way it was supposed to anyway.

Before:

```js
var deferred = $q.defer();
var User = $resource('/api/user/:id', {id: '@id'}, {
  get: {method: 'GET', timeout: deferred.promise}
});

var user = User.get({id: 1});   // sends a request
deferred.resolve();             // aborts the request

// Now, we need to re-define `User` passing a new promise as `timeout`
// or else all subsequent requests from `someAction` will be aborted
User = $resource(...);
user = User.get({id: 2});
```

After:

```js
var User = $resource('/api/user/:id', {id: '@id'}, {
  get: {method: 'GET', cancellable: true}
});

var user = User.get({id: 1});   // sends a request
instance.$cancelRequest();      // aborts the request

user = User.get({id: 2});
```

Fixes #9332
Closes #13050
Closes #13058
Closes #13210