Extensible Liquidity Ads

[t-bast]

The initiator of open_channel2, tx_init_rbf and splice_init can request funding from the remote node. The non-initiator node will:

• let the open-channel-interceptor plugin decide whether to provide liquidity for new channels or not, and how much
• always honor liquidity requests on existing channels (RBF and splice) when funding rates have been configured

Liquidity ads are included in the node_announcement message, which lets buyers compare sellers and connect to sellers that provide rates they are comfortable with. They are also included in the init message which allows providing different rates to specific peers.

This implements lightning/bolts#1153. We currently use the temporary tlv tag 1339 while we're waiting for
feedback on the spec proposal.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 93.81443% with 24 lines in your changes missing coverage. Please review.

Project coverage is 86.06%. Comparing base (14a4ea4) to head (c77ff37).
Report is 11 commits behind head on master.

Files with missing lines	Patch %	Lines
...re/src/main/scala/fr/acinq/eclair/NodeParams.scala	50.00%	9 Missing ⚠️
...inq/eclair/channel/fsm/ChannelOpenDualFunded.scala	90.00%	5 Missing ⚠️
...a/fr/acinq/eclair/wire/protocol/LiquidityAds.scala	92.18%	5 Missing ⚠️
.../main/scala/fr/acinq/eclair/db/DualDatabases.scala	0.00%	4 Missing ⚠️
...main/scala/fr/acinq/eclair/db/DbEventHandler.scala	50.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2848      +/-   ##
==========================================
+ Coverage   85.98%   86.06%   +0.08%     
==========================================
  Files         219      220       +1     
  Lines       18538    19015     +477     
  Branches      786      818      +32     
==========================================
+ Hits        15939    16365     +426     
- Misses       2599     2650      +51     

Files with missing lines	Coverage Δ
...r-core/src/main/scala/fr/acinq/eclair/Eclair.scala	56.61% <100.00%> (+0.18%)	⬆️
.../src/main/scala/fr/acinq/eclair/PluginParams.scala	66.66% <ø> (ø)
...in/scala/fr/acinq/eclair/channel/ChannelData.scala	100.00% <ø> (ø)
.../scala/fr/acinq/eclair/channel/ChannelEvents.scala	100.00% <100.00%> (ø)
...c/main/scala/fr/acinq/eclair/channel/Helpers.scala	94.20% <100.00%> (-0.12%)	⬇️
...in/scala/fr/acinq/eclair/channel/fsm/Channel.scala	85.40% <100.00%> (+0.20%)	⬆️
...inq/eclair/channel/fund/InteractiveTxBuilder.scala	92.18% <100.00%> (+0.51%)	⬆️
...cinq/eclair/channel/fund/InteractiveTxFunder.scala	92.90% <100.00%> (+0.42%)	⬆️
...c/main/scala/fr/acinq/eclair/db/pg/PgAuditDb.scala	99.73% <100.00%> (+0.04%)	⬆️
...cala/fr/acinq/eclair/db/sqlite/SqliteAuditDb.scala	99.71% <100.00%> (+0.04%)	⬆️
... and 19 more

... and 5 files with indirect coverage changes