[8.x] Fixes missing lazy() and lazyById() on BelongsToMany and HasManyThrough relation query builder

[crynobone]

Current Behaviour

$user = User::find(1);

foreach ($user->roles()->lazy() as $role) {
     // $role->pivot === null because additional select to retrieve pivot wasn't available
}

Signed-off-by: Mior Muhammad Zaki [email protected]