VIM-210 Fix focus issues with the Ex panel

Previously, if the editor window had been splitted, under certain
conditions some actions related to the Ex panel would cause the editor
focus to change to a different split.

The required conditions for this bug to occur:
    - no docked windows (like the Project sidebar) are open
    - 'View -> Navigation bar' is disabled

At least these actions triggered the bug:
    - search with /
    - successfully executing an Ex command
    - dismissing the Ex window with Esc
    - Ex commands that opened the output panel (e.g. :!)

All the deleted lines of the form
    FileEditorManager.getInstance(project).openFile(vf, true);
seem to be very old, non-functional workarounds for the focus issue.