SERVER-78124: add query count in getPlanCache list, this can help us to get the hot query sql.

[y123456yz]

We have such a problem， When there are a lot of sql queries, some query have more than one candidate index,and have many slow log， maybe index problem, we don't know which index shold be priority optimize.

add the counters, we can get hot sql that have inde problem, this may be useful.