MB-9890: avoid logging states of xdc_vbucket_rep childs

When xdc_vbucket_rep process exits it triggers proc_lib code that
dumps exit reason and other convenience diagnostic. Part of that
diagnostics is dump of neighbor process states that don't trap
exits. And worker sub-processes of xdc_vbucket_rep are such processes
that don't trap exits.

So in order to prevent proc_lib from exposing internals of those
workers, we create them via intermediate processes that do trap exits.

Change-Id: I9a92dacd29fa9655bf840ec4bb225ac6d3b40b45
Reviewed-on: http://review.couchbase.org/42491
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
MB-12210: log xdcr dcp activity to xdcr log

Change-Id: Ida60e2f2910463d93db25a9887e97fb9966cc0da
Reviewed-on: http://review.couchbase.org/42529
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
MB-12210: log initial xdcr replication position to xdcr log

Change-Id: I045aaf78e6362cf9f511de26ef4c21c6887cacaa
Reviewed-on: http://review.couchbase.org/42530
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
MB-12210: log remote_clusters_info activity to xdcr logs

Change-Id: Ie2a313867114c6685c78fc9d618f3601e35bccea
Reviewed-on: http://review.couchbase.org/42531
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
MB-12210: send capi_replication messages to xdcr log

Change-Id: If51a9aad13acdf3e381b3af6b469974d941d1ae9
Reviewed-on: http://review.couchbase.org/42532
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
MB-12210: send xdcr dcp open_connection messages to xdcr log

Change-Id: I2320996042b6ef30c4694b982f78e4939d4be02f
Reviewed-on: http://review.couchbase.org/42533
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
log xdcr replication stint starts and finishes

Change-Id: Ib24a62a14fb4e3a9c0b9e6dcaa6e5272bd293a83
Reviewed-on: http://review.couchbase.org/42534
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>