Propagate outward if else constraint

[JSAbrahams]

Relevant issues

• Closes #367

Summary

Remove unnecessary creation of further sets in the builder in:

• if else
• if

This means that a proper constraint is generated for a whole if statement in the outer set (in which the if is defined). Before, a new set was created meaning that this information was lost when exiting the set right after the if.

Added Tests

Happy

• Re-add test of nested ifs (see #367 )
• Remove test of if_else in generate stage which was too granular.

[codecov[bot]]

Codecov Report

Merging #407 (31baaeb) into develop (dbeb53e) will decrease coverage by 0.01%. The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #407      +/-   ##
===========================================
- Coverage    87.56%   87.54%   -0.02%     
===========================================
  Files          109      109              
  Lines        12035    12019      -16     
===========================================
- Hits         10538    10522      -16     
  Misses        1497     1497              

Impacted Files	Coverage Δ
src/check/constrain/constraint/builder.rs	88.46% <ø> (-0.63%)	:arrow_down:
src/check/constrain/generate/definition.rs	89.86% <ø> (-0.71%)	:arrow_down:
src/check/constrain/generate/control_flow.rs	92.38% <100.00%> (-0.28%)	:arrow_down:
src/check/constrain/mod.rs	71.11% <100.00%> (+1.34%)	:arrow_up: