refactor(mypy): add stricter rules to p2p tests [part IV/VI]

[glevco]

Depends on #972

Motivation

This PR continues to improve the strictness of mypy in test modules. For more info see the first PR in this series, #969.

Acceptance Criteria

• Add stricter mypy rules to tests.p2p module and update it to conform.

Checklist

• If you are requesting a merge into master, confirm this code is production-ready and can be included in future releases as soon as it gets merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.10%. Comparing base (74b7251) to head (b42aa67).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #973      +/-   ##
==========================================
+ Coverage   85.06%   85.10%   +0.04%     
==========================================
  Files         294      294              
  Lines       22800    22801       +1     
  Branches     3435     3435              
==========================================
+ Hits        19394    19405      +11     
+ Misses       2720     2713       -7     
+ Partials      686      683       -3     

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The base branch was changed.