refactor: remove coinbase constructor arg

[enitrat]

Time spent on this PR:

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Resolves #1391

What is the new behavior?

• Removes the COINBASE constructor argument. If not set later, fees will be burnt.

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This change is 

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.9%. Comparing base (87153b8) to head (d256fef).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1438     +/-   ##
=======================================
- Coverage   62.8%   61.9%   -0.9%     
=======================================
  Files         49      44      -5     
  Lines       8386    8169    -217     
=======================================
- Hits        5270    5061    -209     
+ Misses      3116    3108      -8     

Flag	Coverage Δ
	61.9% <ø> (-0.9%)	⬇️

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