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
  * 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
  * Scroll the view with Shift+Up/Down/PgUp/PgDown/Home/End - the view should scroll
  * Split the view, do previous test in each split - only currently active split should scroll
* 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
  * Use IME to enter text - nothing in terminal should be shown

Reviewers: #konsole, hindenburg

Reviewed By: #konsole, hindenburg

Subscribers: hindenburg, #konsole

Tags: #konsole

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

(cherry picked from commit 2e086c85)