Add Cache for Files Using min_bytes_to_use_mmap_io to Improve Performance

Add cache for files read with min_bytes_to_use_mmap_io setting. It makes significant (2x and more) performance improvement when the value of the setting is small by avoiding frequent mmap/munmap calls and the consequent page faults. Note that mmap IO has major drawbacks that makes it less reliable in production (e.g. hung or SIGBUS on faulty disks; less controllable memory usage). Nevertheless it is good in benchmarks. #22206 (alexey-milovidov).