container: Only give a titlebar height for normal borders

[lanodan]

Closes: #7409

[lanodan]

Note that while this respects the documented configuration, interaction with windows having other border settings is quite a mess.

I guess sway should be forcing borders on childs of non-toplevel container with multiple childs.

Probably what's attempted there but failing because a workspace always has a container (and/or title height being queried in a lot of other places):

sway/sway/desktop/transaction.c

Lines 288 to 299 in dcb142b

	static void arrange_children(enum sway_container_layout layout, list_t *children,
	struct sway_container *active, struct wlr_scene_tree *content,
	int width, int height, int gaps) {
	int title_bar_height = container_titlebar_height();
	if (layout == L_TABBED) {
	struct sway_container *first = children->length == 1 ?
	((struct sway_container *)children->items[0]) : NULL;
	if (config->hide_lone_tab && first && first->view &&
	first->current.border != B_NORMAL) {
	title_bar_height = 0;
	}