Rustfmt ChannelManager splice message handlers

[wpaulino]

Should we squash all the rustfmt commits into one to keep the git history tidier?

[ldk-reviews-bot]

I've assigned @tankyleo 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 52.07756% with 173 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.06%. Comparing base (2647583) to head (fb6d61a).
⚠️ Report is 11 commits behind head on main.

Files with missing lines	Patch %	Lines
lightning/src/ln/channelmanager.rs	49.56%	159 Missing and 14 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4412      +/-   ##
==========================================
+ Coverage   86.05%   86.06%   +0.01%     
==========================================
  Files         156      156              
  Lines      103384   103454      +70     
  Branches   103384   103454      +70     
==========================================
+ Hits        88971    89042      +71     
+ Misses      11900    11896       -4     
- Partials     2513     2516       +3     

Flag	Coverage Δ
tests	86.06% <52.07%> (+0.01%)	⬆️

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[TheBlueMatt]

There's random formatting in the first two prefactors which is weird.

[wpaulino]

There's random formatting in the first two prefactors which is weird.

That's because the formatter wasn't actually being applied due to the inlined macro call.