[5.8] Refactor DELETE query bindings

[staudenmeir]

We have to remove select bindings from DELETE queries to fix cases like this:

class Post extends Model
{
    protected $withCount = ['comments'];

    public function comments()
    {
        return $this->morphMany(Comment::class, 'commentable');
    }
}

Post::where('id', 1)->delete();

// expected
delete from "posts" where "id" = 1

// actual
delete from "posts" where "id" = 'App\Post'

#22285 fixed this for MySQL, #22298 for SQLite.

#22285 also put join bindings first, but that's not necessary. They always come before where bindings.

This PR removes the unnecessary code and moves the fix up to the parent class. This also fixes queries on PostgreSQL and SQL Server.

[oliverquynh]

Nice!

[driesvints]

Removing the public methods is technically a breaking change. Maybe mark them as deprecate them in this PR and remove them in a separate PR to master?

[staudenmeir]

@driesvints I don't see how this could be a breaking change. I'm not removing the method, the parent implementation still exists.

[driesvints]

@staudenmeir I see. Sorry, I didn't realize that. This isn't indeed isn't a breaking change.