[FEATURE] Integ test and bwc test for both approximate and exact search

[heemin32]

Currently, the k-NN query performs either approximate or exact searches, determined by complex internal logic. In the existing integration and backward compatibility (BWC) tests, each test is written once without explicitly considering whether the query runs in exact or approximate search mode. To improve test coverage, we should set up two distinct environments: one for approximate search and another for exact search, and execute the same tests in both environments.