Rename all the helpers specific to the flushing operations to make it
clear that the intention is to flush all created subflows, and remove
all announced addresses, not just a specific selection.

That way, it is easier to understand why the id_avail_bitmap and
local_addr_used are reset at the end.
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20240902-net-next-mptcp-mib-mpjtx-misc-v1-1-d3e0f3773b90@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>