[12.x] Fix for global autoload relationships not working in certain cases

[litvinchuk]

Fix for #55438 issue

In the current implementation of #53655, Model::automaticallyEagerLoadRelationships does not work in certain cases.

For example:

Model::automaticallyEagerLoadRelationships();

class Project extends Model
{
    public function contracts()
    {
        return $this->belongsToMany(Contract::class);
    }
}

# Autoloading works fine here
foreach ($project->contracts as $contract) {
    $contractors[] = $contract->contractor;
}

# Not working — we have an N+1 issue here
foreach ($project->contracts()->get() as $contract) {
    $contractors[] = $contract->contractor;
}

After this fix, both scenarios work as expected.