Struct-ify reconnect_nodes test util args

[valentinewallace]

Makes it easier to add new arguments without a ton of resulting test changes. Useful for route blinding testing because we need to check for malformed HTLCs, which is not currently supported by reconnect_nodes. It also makes it easier to tell what is being checked in relevant tests.

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01% 🎉

Comparison is base (5cddf5e) 90.32% compared to head (ece4db6) 90.34%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2459      +/-   ##
==========================================
+ Coverage   90.32%   90.34%   +0.01%     
==========================================
  Files         106      106              
  Lines       55732    55781      +49     
  Branches    55732    55781      +49     
==========================================
+ Hits        50342    50397      +55     
+ Misses       5390     5384       -6     

Files Changed	Coverage Δ
lightning/src/ln/chanmon_update_fail_tests.rs	98.69% <100.00%> (+<0.01%)	⬆️
lightning/src/ln/functional_test_utils.rs	88.83% <100.00%> (-0.09%)	⬇️
lightning/src/ln/functional_tests.rs	98.26% <100.00%> (+<0.01%)	⬆️
lightning/src/ln/onion_route_tests.rs	98.50% <100.00%> (ø)
lightning/src/ln/payment_tests.rs	97.66% <100.00%> (+<0.01%)	⬆️
lightning/src/ln/reload_tests.rs	95.69% <100.00%> (+0.02%)	⬆️

... and 3 files with indirect coverage changes

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