Skip collateral return if it is too small

[cffls]

Stop txbuilder from creating collateral return when the return amount is below a threshold (default 1ADA).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.09%. Comparing base (d7d2053) to head (3327496).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #411      +/-   ##
==========================================
+ Coverage   88.08%   88.09%   +0.01%     
==========================================
  Files          32       32              
  Lines        4204     4210       +6     
  Branches     1048     1050       +2     
==========================================
+ Hits         3703     3709       +6     
  Misses        349      349              
  Partials      152      152              

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