Four panes had grown the same dance around ratatui's table: clamp the
selection, take the visible page, hand the table a page-local state,
keep the page start. It is now page_window and render_page in a paging
module beside page_of, and the two popups page by the same count they
draw, tab bar or header included.
Five typed filters had grown the same key handling too. edit_filter now
takes a key for all of them, which also stops a control or alt chord
from typing its letter into a filter, stops Enter, which keeps a filter,
from resetting the view it is over, and lets the results and room-list
filters page like the others. Their titles and the typing shortcuts
come from one place as well.
