Add interpreter tests for common resource reference usages

[turbolent]

Description

Add additional tests that I had written for an earlier fix where the result variable in post-conditions was changed to be a reference if the result type is a resource (#905).

The tests show that post-conditions existing on Mainnet keep working, i.e. ones that access members, and that use isInstance with a resource type.

This is a port of a part of dapperlabs/cadence-internal#9

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• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[codecov-commenter]

Codecov Report

Merging #916 (4c892b3) into master (ca1e640) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #916   +/-   ##
=======================================
  Coverage   40.17%   40.17%           
=======================================
  Files         254      254           
  Lines       31882    31882           
=======================================
  Hits        12808    12808           
  Misses      18207    18207           
  Partials      867      867           

Flag	Coverage Δ
unittests	40.17% <ø> (ø)

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