Add query filter generic to `Res` and `ResMut`

## What problem does this solve or what need does it fill?

Now that resources are components we can use a lot of the features of queries with them. Unfortunately the only way you can use them is by avoiding `Res` and `ResMut` which makes it difficult for new users to find.

```rust
fn change_level_single(level: Single<&Level, Changed>) {
match level.0 {
...
}
}

// Note: This requires knowledge of `Populated`. Using `Query` will work, but doesn't skip if parameter cannot be found, which could make certain things harder.
fn change_level_query(level: Res, changed: Populated<() Changed>) {
match level.0 {
...
}
}
```

## What solution would you like?

Add query filters to `Res` and `ResMut`

```rust
fn change_level(level: Res>) {
match level.0 {
...
}
}
```

## What alternative(s) have you considered?

Continue to work with what we have, and improve `Res`/`ResMut` docs.