CI revealed one:

```
cc plugins/libplugin-pay.c
plugins/libplugin-pay.c: In function ‘payment_getroute’:
plugins/libplugin-pay.c:888:17: error: ‘errstr’ may be used uninitialized [-Werror=maybe-uninitialized]
  888 |                 payment_fail(p, "%s", errstr);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
plugins/libplugin-pay.c:851:21: note: ‘errstr’ was declared here
  851 |         const char *errstr;
      |                     ^~~~~~
cc1: all warnings being treated as errors
```

My local compiler gave another:

```
channeld/channeld.c: In function ‘resume_splice_negotiation’:
channeld/channeld.c:3734:23: error: ‘final_tx’ may be used uninitialized [-Werror=maybe-uninitialized]
 3734 |                 msg = towire_channeld_splice_confirmed_signed(tmpctx, final_tx,
      |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 3735 |                                                               chan_output_index);
      |                                                               ~~~~~~~~~~~~~~~~~~
channeld/channeld.c:3461:28: note: ‘final_tx’ was declared here
 3461 |         struct bitcoin_tx *final_tx;
      |                            ^~~~~~~~
cc1: all warnings being treated as errors
make: *** [Makefile:298: channeld/channeld.o] Error 1
```

So fix both.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Created a new canned gossmap without private channels, updated tests.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

This will be used for generating route hints rather than private gossip

and stash in the database.

Rusty: I added the bad gossip message so we would see unknown updates in CI, and made sure we don't send our own generated updates to lightningd.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Not just when it's a private channel.  This is useful for listpeerchannels in the next patch.
Most of this is renaming.

It also means that source can be NULL, so move it out of the struct and put it in the message,
where it logically belongs, and make it an optional field.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

This is redundant if it's a public channel, but vital if it's not.  Publishing unconditionally makes
it easier for gossmap: we create a local modification all the time, even if redundant (and we can
have the actual capacity ceiling accurate in this case, since we know it for local channels).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Changelog-Added: JSON-RPC: `listpeerchannels` now shows gossip update contents (even if channel unannounced).

…ent fee info.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

This lets us convert one user at a time.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

…pdates.

This is more thorough than the minimal one required for getroute(), including the feerates
and cltv deltas.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

…suppression.

We have multiple different routines here, and we want to wean them off private
gossip one at a time.  This converts `getroute`.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

…rivate gossip_store records.

[ Includes use-after-free fix from Alex Myers <alex@endothermic.dev> ]

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

This will become important when we apply localmods to the gossmap at these points.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

…ssip_store records.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

We can, but I had a typo and thought we couldn't!

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

We will get localmods from gossmods_from_listpeerchannels in the next commit,
so we need to save routehints to add to that later.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

…e gossip_store records.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

l2 gave us a routehint, but it should have seen l1 as a dead-end.  It
didn't due to the presence of a channel alias, which was a bug.  We're
about to fix this, which breaks the test.

Add a dummy node off l1.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

This is wrong, but we send them for now in zeroconf!

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

We temporarily use a second gossmap so we can just switch private info off
for listincoming and not listchannels.

Note that listchannels now uses the local alias (if no scid), so we have
to change that in the routehint caller.

Since we now *always* use a channel alias in hints if one exists, a
test broke, so fix that.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Now listincoming sees local channels in listpeerchannels, we don't need these waits.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

This breaks our tests a bit, which assumed we can always see ourselves
even if we don't have a proper channel.

Usually we would deprecate this first, but it's unlikely to break
anyone since it's a bit obscure that this worked at all.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Changed: JSON-RPC: `listnodes` no longer shows private (peer) nodes: use listpeers

… private gossip.

Some can only be changed once that is true, but some can be removed/amended already.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

This alters a few remaining tests, as well.

[ Inclused even more test fixes from Alex Myers <alex@endothermic.dev>! ]

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Deprecated: JSON-RPC: `listchannels` listing private channels: use listpeerchannels

In the next PR, they'll be removed, but for now all our code doesn't
want them.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

…eerchannels` info.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Deprecated: `listchannels` no longer uses local knowledge to set `active` to false if disconnected.

We only deprecated this, we didn't actually remove it.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>