qtconsole: Add vi-like key bindings to pager (fixes #6590)

Since _event_fileter_page_keypress() already exists in ConsoleWidget
class of qtconsole, that change was pretty easy and isolated. We emulate
up/down arrow keys with k/j when we use pager.
Merge pull request #6643 from JIghtuse/upstream

qtconsole: Add vi-like key bindings to pager (fixes #6590)