Merge branch 'rnou/opt' into 'master'

Fixes and optimizations

This MR solves:
* Malleability issues due a put instead a update on rocksdb on metadata movements (old stale metadata status could survive)
* Malleability tool : gkfs_malleabiliy mutate sync command : Synchronously traverses all the malleability phases
* Add a weight + benchmark phase before the daemons are ready so the servers are weighted per write bandwidth. It can even decide to go to memory (or a secondary root) if we hit a threshold
* Needs Random Slicing and GKFS_RANDOM_SLICING_CALIBRATION and ( GKFS_DAEMON_2ND_ROOT with GKFS_RANDOM_SLICING_MIN_MBPS , optional )

See merge request !320