bug: In bpm_bench.cpp, two get_threads may check the consistency of the same page.

[yuerdong]

bustub/tools/bpm_bench/bpm_bench.cpp

Line 265 in d5f7943

auto page_idx = std::min(rand / get_thread_n * get_thread_n + thread_id, bustub_page_cnt - 1);

If bustub_page_cnt is not divisible by get_thread_n, this line may cause two different threads getting the same page_id. As a result, bpm_bench may report "page seed not consistent", despite the fact that the buffer pool is implemented correctly. I have passed all the tests on gradescope, but bpm_bench fails once I change get_thread_n from 8 to 9.