test(chain): test chain economics processor

[frrist]

This feels like a lot of typing for little reward. For now I'm wanting try this with github.com/stretchr/testify/mock but remain open to alternatives.

[codecov-io]

Codecov Report

Merging #297 (d585491) into master (4021e6c) will decrease coverage by 1.1%.
The diff coverage is 14.2%.

@@           Coverage Diff            @@
##           master    #297     +/-   ##
========================================
- Coverage    45.2%   44.0%   -1.2%     
========================================
  Files          19      20      +1     
  Lines        1897    1971     +74     
========================================
+ Hits          859     869     +10     
- Misses        925     987     +62     
- Partials      113     115      +2     

[iand]

I think the mock of the lens is valuable, as is reducing the node api to a smaller interface. We should always be writing code that accepts the smallest possible interface anyway.

However, much of this code is going to be redundant as soon as we move away from the random access approach used by the run command. LeaseTipSetEconomics and MarkTipSetEconomicsComplete won't be needed and the chain economics extraction interface becomes a lot simpler.

Currently have a second implementation of chain economics extraction in the chain package, which I expect to become the primary. I'm going to spend some time today to try and reduce that duplication by refactoring extractChainEconomicsModel to export it.

[iand]

See #298 for a refactoring based on this

[frrist]

Closing in favor of #298. I appreciate the help here @iand