Summary:
This PR fixes a bug in how MultiScan handled a scan range limit falling in the key range between files. The bug was in LevelIterator, where Prepare() relied on FindFile to determine the lower bound file for the range limit. FindFile returns the smallest file index with `range.limit < file.largest_key`. However, that doesn't guarantee that the range overlaps the file, as the `range.limit` could be smaller than `file.smallest_key`.
This also fixes a bug in BlockBasedTableIterator of Valid() returning true even if status() returned error. This was exposed by the previous bug.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/14011
Test Plan: Add unit tests in db_iterator_test and table_test
Reviewed By: cbi42
Differential Revision: D83496439
Pulled By: anand1976
fbshipit-source-id: a9d2d138d69d0c816d9f4160a984b273d00d683f
b4a3612256