This reverts commit ab8b80944967ee5a6a0c45dbf61839cf257bfe44.

- Move test-only cpath_get_n_hops() to crypt_path.c.
- Move onion_next_hop_in_cpath() and rename to cpath_get_next_non_open_hop().

The latter function was directly accessing cpath->state, and it's a first step
at hiding ->state.

Some of these functions are now public and cpath-specific so their name should
signify the fact they are part of the cpath module:

assert_cpath_layer_ok -> cpath_assert_layer_ok
assert_cpath_ok -> cpath_assert_ok
onion_append_hop -> cpath_append_hop
circuit_init_cpath_crypto -> cpath_init_circuit_crypto
circuit_free_cpath_node -> cpath_free
onion_append_to_cpath -> cpath_extend_linked_list

Now that we are using a constructor we should be more careful that we are
always using the constructor to initialize crypt_path_t, so make sure that
->private is initialized.

We are using an opaque pointer so the structure needs to be allocated on the
heap. This means we now need a constructor for crypt_path_t.

Also modify all places initializing a crypt_path_t to use the constructor.

Again everything is moved, apart from a free line using ->private.

Everything is moved, but the argument of the function is edited to access
->private->crypto.

Create some functions to eventually be able to hide crypt_path_t.crypto.

This commit only moves code.

This commit only moves code, and makes one function public.

This will be our base for incrementally hiding crypt_path_t.

Signed-off-by: David Goulet <dgoulet@torproject.org>

"ours" to avoid version bump.

Signed-off-by: David Goulet <dgoulet@torproject.org>

This mechanism isn't perfect, and sometimes it will guess wrong,
but it will help our automation.

For various reasons, this was a nontrivial movement.  There are
several places in the code where we do something like "update the
flags on this routerstatus or node if we're an authority", and at
least one where we pretended to be an authority when we weren't.

Signed-off-by: David Goulet <dgoulet@torproject.org>

"ours" to avoid version bump