Use the fee rate in oubound channel to calculate the TLC fee

[contrun]

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 91.56627% with 7 lines in your changes missing coverage. Please review.

Project coverage is 50.47%. Comparing base (8725983) to head (46ac31e).
Report is 2 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/fiber/channel.rs	87.75%	6 Missing ⚠️
src/fiber/graph.rs	96.87%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #489      +/-   ##
===========================================
+ Coverage    50.41%   50.47%   +0.05%     
===========================================
  Files           49       49              
  Lines        31824    31858      +34     
===========================================
+ Hits         16045    16080      +35     
+ Misses       15779    15778       -1     

Flag	Coverage Δ
unittests	50.47% <91.56%> (+0.05%)	⬆️

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[gpBlockchain]

LGTM