Bug: When deleting files or entering folders with multibyte characters, the app might crash

[imsnif]

The original issue was reported (along with a PR) here: #51
This fixes the issue for tiles on the board (the filenames in the rectangle grid), but we would also need to fix this:

error_box
title_telescope
bottom_line

• for folders we enter and the base folder (in the title bar): src/ui/title/title_telescope.rs (I think a change here would suffice:

  diskonaut/src/ui/title/title_telescope.rs

  Line 186 in 120058d

  current_position += truncated_cell.chars().count() as u16;

  )

• for file display in the bottom lines: src/ui/bottom_line.rs (especially in render_currently_selected and render_last_read_path)

• in deletion confirmation and error message boxes: src/ui/modals/error_box.rs and src/ui/modals/message_box.rs

@goto-bus-stop, I'm assigning this to you since you said you'd like to work on this when you have time. Good catch on these!