Add check of Consumption BEN_*_value parameters

[martinholmer]

This pull request adds to the Calculator distribution_tables and difference_table methods a check that the two Calculator objects have the same values for the BEN_*_value parameters embedded in their Consumption objects. This test is necessary because the consumption value of non-cash benefits is included in expanded_income. Different values for the BEN_*_value parameters in the baseline and reform Calculator objects would induce a spurious change in both expanded_income and after-tax expanded income.

[codecov-io]

Codecov Report

Merging #1894 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #1894   +/-   ##
======================================
  Coverage     100%    100%           
======================================
  Files          37      37           
  Lines        3301    3308    +7     
======================================
+ Hits         3301    3308    +7

Impacted Files	Coverage Δ
taxcalc/consumption.py	100% <100%> (ø)	⬆️
taxcalc/calculate.py	100% <100%> (ø)	⬆️

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