OptionChangeMigration() to support FIFO compaction

OptionChangeMigration() to support FIFO compaction

Summary: OptionChangeMigration() to support FIFO compaction. If the DB before migration is using FIFO compaction, nothing should be done. If the desitnation option is FIFO options, compact to one single L0 file if the source has more than one levels.

Test Plan: Run option_change_migration_test

Reviewers: andrewkr, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D65289