revert: Even more quick way to switch to a previous document

This commit introduced too many regressions, e.g. the action View >
Quick Open did not work anymore

Revert:
Even more quick way to switch to a previous document: show opened docs
list (project files) only if user holds a `Ctrl` for awhile (~200ms),
otherwise just quick-quick-switch to a previous document w/o flikering
w/ widgets...

CCBUG: 324348