Removed destination-is-ancestor check from container_move_to_container to match i3 behaviour

[ccdunder]

Closes #6818

This extracts the specific part of #6835 that addresses the issue. I'm doing this since the original PR was closed over 2 years ago after the author got informal approval for this part of the change but pushback on other parts (not included here).

It removes this line

sway/sway/commands/move.c

Line 235 in f707f58

|| container_has_ancestor(container, destination)

In order to match the behaviour of i3's move functionality, which can be found here, posted below:

    /* We compare the focus order of the children of the lowest common ancestor. If con or
     * its ancestor is before target's ancestor then con should be placed before the target
     * in the focus stack. */
    Con *lca = lowest_common_ancestor(con, parent);
    if (lca == con) {
        ELOG(\"Container is being inserted into one of its descendants.\
\");
        return;
    }

Basically, sway is checking on move that a destination is neither a descendant of the container to be moved, and that the container to be moved is not a descendant of the destination, whereas i3 only (rightly, I think) checks that the destination is not a descendant, as such a lot of valid moves in i3 simply don't work in sway and this fixes that.

[Nefsen402]

Thanks!