In Vim's main_loop function, the main loop is

        while (!cmdwin
    #ifdef FEAT_CMDWIN
                || cmdwin_result == 0
    #endif
                )
        {
    ...
    #ifdef FEAT_EVAL
            /*
             * May perform garbage collection when waiting for a character, but
             * only at the very toplevel.  Otherwise we may be using a List or
             * Dict internally somewhere.
             * "may_garbage_collect" is reset in vgetc() which is invoked through
             * do_exmode() and normal_cmd().
             */
            may_garbage_collect = (!cmdwin && !noexmode);
    #endif
            /*
             * If we're invoked as ex, do a round of ex commands.
             * Otherwise, get and execute a normal mode command.
             */
            if (exmode_active)
            {
                if (noexmode)   /* End of ":global/path/visual" commands */
                    return;
                do_exmode(exmode_active == EXMODE_VIM);
            }
            else
                normal_cmd(&oa, TRUE);
        }

cmdwin_result is set to 0 before calling main_loop to handle the cmdwin
window and gets changed when the user causes a command to execute
(either through pressing <CR> or <C-c>).  This means that when the
cmdwin isn't active OR the user is still editing their command,
main_loop runs and main_loop calls normal_cmd with toplevel true as long
as exmode isn't active.

When the normal mode state was extracted in dae006a9, the conditions for
toplevel and may_garbage_collect were combined.  Since toplevel was set
to always ignore cmdwin, the v:count(1) variables were no longer being
updated when a command was prefixed with a count in the cmdwin.

Closes #5404

It is otherwise impossible to determine which test failed sanitizer/valgrind
check. test/functional/helpers.lua module return was changed so that tests which
do not provide after_each function to get new check will automatically fail.