Refactoring & conflict fixes

[diskree]

Huh?

Hello! I'm making a mod that also makes changes to the GUI of the book, and I had a mixin conflict. The problem is that your code is currently doing more than it should. Instead of changing the code associated with the Y coordinate, your mod overwrites some of the vanilla code in different places. This is what bothered me, so I decided to open this pull request.

Changes

• Instead of changing the Y coordinate for all UI components separately, I move the matrices using translate(x, y) method. Thanks to this we shift the entire interface.
• Instead of duplicating ButtonWidget.Builder code we shift only what we need - the Y coordinate.
• More readable code and method order in mixins.
• The method that returns Y relative to the screen has been moved to the FixBookGui, instead of being duplicated in 3 mixins.
• For the new code it was necessary to add accesswidener to access some closed Vanilla code.

[diskree]

Oops. Incorrect branch :) I will be reopen pr