The tests would leave the following test files in the root directory:

    Xtest-functional-plugin-shada.shada
    Xtest-functional-plugin-shada.shada.tmp.f

Clean them up in teardown().

shada: Do not save unlisted and quickfix buffers

Store last search direction when writing ShaDa files

Note: it looks like viminfo files do not store search direction intentionally.
After reading viminfo file search direction was considered to be “forward”.

Note 2: all files created on earlier Neovim version will automatically receive
“forward” direction.

Fixes #3580

The focus event tests now live in their own `describe` block with each
test testing the handling of focus events in a single mode.

This change adds switch cases for K_FOCUSGAINED and K_FOCUSLOST to the
input handling functions in ex_getln.c and terminal.c. The handling is
identical to what's found in edit.c (just calling apply_autocmds).

If one enters cmdline-mode by feeding `:` and sends a focuslost event (by
leaving the window for example) the text `<FocusLost>` will be inserted
into the command line. There is similar behaviour in terminal mode. This
patch corrects this behavior to fire the apropriate autocmd instead.

Fixes #3714

Fixes #3635

Add plugin for editing ShaDa files