Convert several unit tests from SCons to Bazel, selected from this document.

Converts the following libraries:

• async_command_execution_test
• commands_test_example
• dbcheck_test_fixture
• fle_mocks
• oplog_interface_mock
• query_planner_test_fixture
• query_planner_test_lib
• sessions_collection_mock

Converts the following unit tests:

• change_collection_test
• command_mirroring_test
• command_test
• db_base_test
• db_commands_test
• default_baton_test
• express_execution_test
• mongod_options_test
• query_test
• session_test

(more targets may be added here while the ticket is in progress)