[Searchable Snapshot] Add Integ test to make there is no resource leak

[aabukhalil]

Searchable Snapshot and how IndexInput is being used, it has lot of clones, closings and many files handling logic. If we missing closing any file then we will cause resource leaks. We Integ test to make sure there is no resource leak. This is possible (theoretically) by creating remote backed index, do some searches, and then delete the index. And monitor the file descriptor held by process affecting the caching directory.

[aabukhalil]

this is estimated as 3 points