fix: Var size when using new type objects

[iamdefinitelyahuman]

What I did

In VariableRecord, return the correct size when the related type object is one of the new context types.

This fixes an issue with memory corruption caused by excessive deallocation when releasing internal variables :(

Cute Animal Picture

[fubuloubu]

Add a test case that shows the incorrect behavior is caught

[codecov-io]

Codecov Report

Merging #2321 (ac651a3) into master (418c85b) will decrease coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2321      +/-   ##
==========================================
- Coverage   85.84%   85.77%   -0.07%     
==========================================
  Files          85       85              
  Lines        8582     8583       +1     
  Branches     2054     2054              
==========================================
- Hits         7367     7362       -5     
- Misses        732      738       +6     
  Partials      483      483              

Impacted Files	Coverage Δ
vyper/signatures/function_signature.py	87.69% <100.00%> (+0.09%)	⬆️
vyper/parser/memory_allocator.py	67.74% <0.00%> (-9.68%)	⬇️

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