EBLOB_AUTO_INDEXSORT eblob flag

New EBLOB_AUTO_INDEXSORT flag which enables sorting blob's index after the blob is closed. Extended running eblob_stress with EBLOB_AUTO_INDEXSORT flag.

Also added stat_file_time and stat_file_error to json statistics which can be used for determining hardware issues.
Why is it only removal? What about overwrite which makes file size smaller?