MB-10273 Merge multiple delta files for view compactor

If there are multiple delta log files in the log apply phase of
compactor, it results in multiple snapshots being created and
results in higher fragmentation.

Made the view compactor delta log apply phase to use a native
delta log file merger to deduplicate-merge multiple log files for
each btree to be merged into one log file and apply that log file
instead of applying multiple files one by one.

Change-Id: If3ad629e06fc0aaba97cdbba68db9bc27dd56bb3
Reviewed-on: http://review.couchbase.org/36264
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>