resource manager trait and impl

[elnosh]

Part of #4384

This PR introduces a ResourceManager trait and DefaultResourceManager implementation of that trait which is based on the proposed mitigation in lightning/bolts#1280.

It only covers the standalone implementation of the mitigation. I have done some testing with integrating it into the ChannelManager but that can be done separately. As mentioned in the issue, the resource manager trait defines these 4 methods to be called from the channel manager:

• add_channel
• remove_channel
• add_htlc
• resolve_htlc

Integrating into the ChannelManager

• The ResourceManager is intended to be internal to the ChannelManager rather than users instantiating their own and passing it to a ChannelManager constructor.

• add/remove_channel should be called when channels are opened/closed.

• add_htlc: When processing HTLCs, the channel manager would call add_htlc which returns a ForwardingOutcome telling it whether to forward or fail the HTLC along with the accountable signal to use in case that it should be forwarded. For the initial "read-only" mode, the channel manager would log the results but not actually fail the HTLC if it was told to do so. A bit more specific on where it would be called: I think it will be when processing the forward_htlcs before we queue the add_htlc to the outgoing channel

  rust-lightning/lightning/src/ln/channelmanager.rs

  Line 7650 in caf0aac

  if let Err((reason, msg)) = optimal_channel.queue_add_htlc(

• resolve_htlc: Used to tell back the ResourceManager the resolution of an HTLC. It will be used to release bucket resources and update reputation/revenue values internally.

This could have more tests but opening early to get thoughts on design if possible

cc @carlaKC

[ldk-reviews-bot]

👋 Thanks for assigning @carlaKC as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

[codecov]

Codecov Report

❌ Patch coverage is 95.13837% with 65 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.16%. Comparing base (94d1e5e) to head (53a93ed).
⚠️ Report is 39 commits behind head on main.

Files with missing lines	Patch %	Lines
lightning/src/ln/resource_manager.rs	95.13%	33 Missing and 32 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4409      +/-   ##
==========================================
+ Coverage   86.03%   86.16%   +0.13%     
==========================================
  Files         156      157       +1     
  Lines      103091   104721    +1630     
  Branches   103091   104721    +1630     
==========================================
+ Hits        88690    90235    +1545     
- Misses      11891    11940      +49     
- Partials     2510     2546      +36     

Flag	Coverage Δ
tests	86.16% <95.13%> (+0.13%)	⬆️

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