Properly handle mouse in read-only mode

Summary:

• Do not send mouse events and emulated up/down keys to programs when read-only mode is enabled.
• Set the currentTerminalDisplay before sending key events, like in keyPressEvent.
• wheelEvent code is restructured a bit to easily separate code not allowed in read-only mode.

Test Plan:

• Start Konsole
• Run man man, do not press any key after enter
• Turn on read only mode
• Try to scroll using mouse wheel.
• Expected result: scrolling does not work in read-only mode
• Actual result: scrolling works in read only mode (but only when no key has been pressed before on 2nd terminal screen)

• Start konsole
• Run a program which uses mouse events, e.g. vim (enable mouse with :set mouse=a)
• Make the program state suitable for using mouse events, e.g. enter a few lines of text
• Confirm that mouse events (clicks, selection, wheel) work in the program
• Turn on read-only mode
• Try:
  • Click (left/right/middle button), double click
  • Mouse wheel
  • Click and move (selecting)
• Expected result: mouse events are not passed to the program in read-only mode; nothing happens
• Actual result: mouse events are passed to the program

Reviewers: Konsole, hindenburg

Reviewed By: Konsole, hindenburg

Subscribers: hindenburg, Konsole

Tags: Konsole

Differential Revision: https://phabricator.kde.org/D11763