Consider many first-hop paths to the same counterparty in routing

[TheBlueMatt]

Previously we'd simply overwritten "the" first hop path to each
counterparty when routing, however this results in us ignoring all
channels except the last one in the ChannelDetails list per
counterparty.

[TheBlueMatt]

Note that this was a user-reported bug, so tagging it 0.0.102 to keep the "user reported bugs get fixed w/i one release" deadline.

[codecov]

Codecov Report

Merging #1100 (cc70446) into main (ad819ea) will decrease coverage by 0.05%.
The diff coverage is 96.49%.

@@            Coverage Diff             @@
##             main    #1100      +/-   ##
==========================================
- Coverage   90.64%   90.58%   -0.06%     
==========================================
  Files          65       65              
  Lines       34226    34549     +323     
==========================================
+ Hits        31024    31297     +273     
- Misses       3202     3252      +50     

Impacted Files	Coverage Δ
lightning/src/routing/router.rs	96.03% <96.49%> (+0.03%)	⬆️
lightning-block-sync/src/lib.rs	93.49% <0.00%> (-1.69%)	⬇️
lightning-net-tokio/src/lib.rs	76.69% <0.00%> (-0.59%)	⬇️
lightning-block-sync/src/http.rs	93.30% <0.00%> (-0.22%)	⬇️
lightning/src/ln/functional_tests.rs	97.47% <0.00%> (+0.04%)	⬆️
lightning/src/util/events.rs	32.07% <0.00%> (+0.07%)	⬆️
lightning/src/ln/channelmanager.rs	85.50% <0.00%> (+0.63%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ad819ea...cc70446. Read the comment docs.

[valentinewallace]

One q but seems legit and test fails as expected on main

[valentinewallace]

Looks fan-tastic

[arik-so]

Looks good to me. Only change I'd wish for is a more descriptive macro name than add_entry.

[TheBlueMatt]

Only change I'd wish for is a more descriptive macro name than add_entry.

I'll let someone else tackle that in a followup - get_route needing some additional clarity isn't a new issue, I think.