osd: EC Optimizations: Share pwlc between peers

osd: EC Optimizations: Share pwlc between peers

Optimized EC pools add partial_writes_last_complete (pwlc) data to
pg_info_t to track shards that were not updated because of partial
writes. During peering the primary collects the info structure from
all the replica/strays and then having reconciled the log can send
the info back to peers. Different shards may have newer/older
versions of pwlc, the primary merges these together to create
the definitive copy and then redistributes this to the other shards.

The primary also adjusts the last_update and last_complete values
in the info structure received from peers using the pwlc data to
advance these where shards were not updated because of a partial
write.

Signed-off-by: Bill Scales <bill_scales@uk.ibm.com>