Fix EventHandlerLoaderTest failing after PojoSerializerLoaderTest

[M-Elsaeed]

Issue #, if available: EventHandlerLoaderTest fails when run after PojoSerializerLoaderTest.

Description of changes: EventHandlerLoaderTest fails when run after PojoSerializerLoaderTest. This was caused by not resetting static fields that were modified by the tests inPojoSerializerLoaderTest after the tests are done.

Target (OCI, Managed Runtime, both): both

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.26%. Comparing base (150b1b7) to head (3a67b65).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main     #542   +/-   ##
=========================================
  Coverage     58.26%   58.26%           
  Complexity      222      222           
=========================================
  Files            46       46           
  Lines          1155     1155           
  Branches        149      149           
=========================================
  Hits            673      673           
  Misses          428      428           
  Partials         54       54           

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