Remove Texture dependency

[denkeni]

Recently I've been doing some internal UI testing to compare scrolling hitches, frame rate, etc. on real devices, e.g. an old one like iPhone SE 1st generation with the latest iOS 15.7.3. I've concluded that Texture does not have major advantage for real-life performance as the old days.

(This project has dropped support for iOS 9-13, i.e. from iPhone 4S to iPhone 6.)

Even though Texture still advances in layout benchmark, Telegram-iOS plans to remove it as well.

I have started to rewrite related code with UIKit, will drop Texture and CocoaPods afterwards. I've contacted with @scsonic that I will be responsible to rewrite related code for login as well.