feat[test]: add more example contracts

[charles-cooper]

What I did

add more example contracts from third party sources. currently, they are just tested for compilations, although we could do some integration / unit tests with them.

How I did it

How to verify it

Commit message

Commit message for the final, squashed PR. (Optional, but reviewers will appreciate it! Please see our commit message style guide for what we would ideally like to see in a commit message.)

Description for the changelog

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.12%. Comparing base (072b386) to head (7666054).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4500      +/-   ##
==========================================
+ Coverage   92.04%   92.12%   +0.07%     
==========================================
  Files         120      120              
  Lines       17361    17361              
  Branches     2940     2940              
==========================================
+ Hits        15980    15993      +13     
+ Misses        964      954      -10     
+ Partials      417      414       -3     

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