Add unit tests for uncovered functionality in the query planner and query solution components.

For current file coverage see the spreadsheet.

Coverage under 80%:

src/mongo/db/query/query_planner_common.cpp

src/mongo/db/query/query_planner.cpp

src/mongo/db/query/query_planner_params.cpp

src/mongo/db/query/query_planner_test_lib.cpp

src/mongo/db/query/query_solution.cpp

src/mongo/db/query/query_solution.h