addresses windows CI failures

[brtnfld]

Binex example tests were failing because they couldn't find plugin DLLs.
Set TEST_ENV_VALUE to ${PROJECT_BINARY_DIR}/../plugins to point tests
to the correct plugin location in the build tree.

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Important

Fixes Windows CI failures by setting environment variables in CMakeLists.txt to locate plugin DLLs.

• Behavior:
  • Sets TEST_ENV_VAR to HDF5_PLUGIN_PATH and TEST_ENV_VALUE to ${PROJECT_BINARY_DIR}/../plugins in CMakeLists.txt to fix Windows CI failures.
  • Ensures tests can locate plugin DLLs in the build tree.
• Testing:
  • Modifies test configurations in CMakeLists.txt to include the new environment variable settings for all relevant tests.
  • Affects multiple test definitions, ensuring consistent environment setup.

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