Refactoring to move page display code into separate class

Idea is to create reusable PDFViewer that will not have dependency on the PDFView (toolbars, find controller, etc).

- [x] Move pages container logic into PDFViewer (?) out of PDFView
- [x] Move thumbs container logic into PDFThumbnailsViewer (?) out of PDFView
- [x] Remove all dependency on PDFView in PDFViewer and classes it's using
- [x] Remove any rendering logic from PDFView
- [x] Isolate PDFPageSource logic and use in PDFViewer, PDFThumbnailsViewer, PDFFindController
- [x] Refactor PresentationMode (minimal, to remove dependency from PDFViewer)

NOTE: The refactoring shall not include any optimization or bug fixes
Fixed. I got confused about strange things we do at https://github.com/mozilla/pdf.js/pull/5295/files#diff-3c5a405b7edf7f3f910c074ab5a703aaL444