This PR refactors the display_list.rs file, which was over 1700 lines, into a more manageable structure by splitting it into separate modules.

Folder structure:

src/renderer/display
├── constants.rs
├── cursor_line.rs
├── display_annotations.rs
├── display_header.rs
├── display_line.rs
├── display_list.rs
├── display_mark.rs
├── display_set.rs
├── display_text.rs
├── end_line.rs
└── mod.rs