Allow view-controlling keys in read-only mode

Summary:
Allow to use scrolling (Shift+Up/Down/PgUp/PgDown/Home/End) and a key
for showing URL hints when the view is in read-only mode.

Test Plan:

• Prepare
  • Turn on scrollback
  • Set at least one modifier key for "Show URL hints" (edit profile → advanced)
  • Generate a few screens of text in Konsole
  • Display some URL (e.g. echo 'www.kde.org')
  • Display current time every second: while sleep 1; do printf '\r%s' "$(date)"; done
  • Turn on read-only mode
• Patch tests
  • Scroll the view with Shift+Up/Down/PgUp/PgDown/Home/End - the view should scroll
  • Hold down URL hint key - the URL should be underlined with square and a digit on the left
  • Press <URL-hint-key>+1 - the URL should open in a web browser
• Regressions tests
  • Press different keys (including Ctrl+C, Ctrl+Z, etc; skip those mapped to Konsole actions) - nothing in terminal should happen
  • Press Ctrl+S - the time should not stop updating

Reviewers: Konsole, hindenburg

Reviewed By: Konsole, hindenburg

Subscribers: hindenburg, Konsole

Tags: Konsole

Differential Revision: https://phabricator.kde.org/D11668

(cherry picked from commit 6635190c1295743e6db3c796892c9fc90fb1f791)