fix(BUX-461) fee quotes for both arc and mAPI with user defined fee quote

[chris-4chain]

Pull Request Checklist

• 📖 I created my PR using provided : CODE_STANDARDS
• 📖 I have read the short Code of Conduct: CODE_OF_CONDUCT
• 🏠 I tested my changes locally.
• ✅ I have provided tests for my changes.
• 📝 I have used conventional commits.
• 📗 I have updated any related documentation.
• 💾 PR was issued based on the Github or Jira issue.

This new version introduces new config field: nodes.fee_unit and moves nodes.mapi.use_fee_quotes to nodes.use_fee_quotes. This change is made because the setting is now applicable to both the ARC and mAPI protocols.

When nodes.fee_unit is defined, it will be used as the offered fee to miners when use_fee_quotes is disabled.
However, by default, use_fee_quotes is enabled, so during the initialization stage, the lowest fee among the fee quotes from configured miners will be selected.

When neither nodes.use_fee_quotes nor nodes.fee_unit is set, the config validation will fail and the application won't start.

Requires new bux version (BuxOrg/bux#533)

[mergify]

Welcome to our open-source project @chris-4chain! 💘

[Nazarii-4chain]

Please check tests

[chris-4chain]

Tests will pass after bux PR and a new release with 0.13.0 version.

[codecov]

Codecov Report

Attention: 12 lines in your changes are missing coverage. Please review.

Comparison is base (85cbe7a) 40.18% compared to head (b5f0a56) 40.61%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #403      +/-   ##
==========================================
+ Coverage   40.18%   40.61%   +0.42%     
==========================================
  Files          46       46              
  Lines        1640     1667      +27     
==========================================
+ Hits          659      677      +18     
- Misses        944      950       +6     
- Partials       37       40       +3     

Flag	Coverage Δ
unittests	40.61% <67.56%> (+0.42%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
config/config.go	100.00% <ø> (ø)
config/defaults.go	100.00% <100.00%> (ø)
config/validate.go	88.00% <0.00%> (-12.00%)	⬇️
config/validate_nodes.go	87.23% <88.00%> (-1.23%)	⬇️
config/services.go	43.77% <25.00%> (-0.07%)	⬇️

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