rustfmt: Run on lightning-persister

[tnull]

We run rustfmt on the lightning-persister crate.

Seems rather straightforward.

[codecov]

Codecov Report

Attention: Patch coverage is 65.02732% with 64 lines in your changes missing coverage. Please review.

Project coverage is 89.68%. Comparing base (43dcf2f) to head (e393893).
Report is 8 commits behind head on main.

Files	Patch %	Lines
lightning-persister/src/fs_store.rs	52.63%	43 Missing and 2 partials ⚠️
lightning-persister/src/utils.rs	42.42%	19 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3222      +/-   ##
==========================================
- Coverage   89.73%   89.68%   -0.05%     
==========================================
  Files         124      124              
  Lines      102376   102498     +122     
  Branches   102376   102498     +122     
==========================================
+ Hits        91869    91930      +61     
- Misses       7813     7868      +55     
- Partials     2694     2700       +6     

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[tnull]

Rebased on main to resolve conflicts.