Short-Term Tolerability of Once-Daily Timolol Hemihydrate 0.5%, Timolol Maleate in Sorbate 0.5%, and Generic Timolol Maleate Gel-Forming Solution 0.5% in Glaucoma and/or Ocular Hypertension: A Prospective, Randomized, Double-Masked, Active-Controlled, Three-Period Crossover Pilot Study