updates with the incoming type lattice overhaul

[aviatesk]

This might not be the cleanest implementation, but on this branch Cthulhu should work with JuliaLang/julia#42596.
I opened this PR as a draft for those who may want to work on the overhaul.

[codecov-commenter]

Codecov Report

Merging #238 (675a16b) into master (af1a2fc) will decrease coverage by 1.27%.
The diff coverage is 28.57%.

@@            Coverage Diff             @@
##           master     #238      +/-   ##
==========================================
- Coverage   82.85%   81.58%   -1.28%     
==========================================
  Files           7        7              
  Lines        1021     1037      +16     
==========================================
  Hits          846      846              
- Misses        175      191      +16     

Impacted Files	Coverage Δ
src/reflection.jl	85.10% <0.00%> (ø)
src/Cthulhu.jl	68.79% <15.00%> (-3.83%)	⬇️
src/codeview.jl	92.14% <50.00%> (-1.34%)	⬇️
src/callsite.jl	78.50% <100.00%> (ø)
src/interpreter.jl	92.00% <100.00%> (ø)

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