get_queried_object is not always working

In https://github.com/alleyinteractive/es-wp-query/commit/bd0033986dfece6017dad4590ab00d13c8023e86 a code allowing `WP_Query::get_posts()` repeated call was introduced, but the `WP_Query::get_posts()` is not strictly idempotent, as there is some backward compatibility related logic and what's more, some query variable evaluation and modification logic which is changing the query_vars property of the class.

Eg.: passing `author_name` query variable leads to setting `author` query variable which is then used for determining the `get_queried_object`. See https://core.trac.wordpress.org/browser/tags/4.7/src/wp-includes/class-wp-query.php#L2121

Example failing code:

```
$my_query = new WP_Query( array( 'author_name' => 'existing-user-slug', 'es' => true ) );
$my_query->get_queried_object(); // Returns `false`.
```

vs.

```
$my_query = new WP_Query( array( 'author_name' => 'existing-user-slug', ) );
$my_query->get_queried_object(); // Returns author object.
```

Also, calling `WP_Query::get_posts()` multiple times, or even creating a new `WP_Query` object while passing query args to the constructor and then calling `WP_Query::get_post()` leads to performance issues in certain cases caused by unnecessarily complex SQL queries - due to the backward compatibility logic.

Again, an example:

```
$my_query = new WP_Query(
array(
'posts_per_page' => 10
'cat' => $some_category_term_id, // This is a legacy query arg which gets extended in WP_Query::get_posts() function.
)
);
$my_query = $latest_posts_query->get_posts(); // This triggers the `WP_Query::get_posts` again, but with moar query variables than just `cat` - those were backfilled during the `$my_query`'s object construction
```

Once the `WP_Query::get_posts()` have been called, either directly or through the constructor of the `WP_Query` when query args were passed to it, the array of posts should be accessed via `WP_Query`'s `posts` property - as it 1) saves a SQL query 2) returns the expected set of posts

@mboynes I wonder, do you have any valid use case for calling `WP_Query::get_posts()` twice or is that just an edge case the plugin covers as developers do sometimes do that, not knowing all the consequences?

I'm asking as in my humble opinion a proper fix for non-working `get_queried_objct` would not be to whitelisting some query variables which are dynamically set, but not resetting those at all. Thoughts?