This commit adds the size of the cluster state to the response for the
get cluster state API call (GET /_cluster/state). The size that is
returned is the size of the full cluster state in bytes when compressed.
This is the same size of the full cluster state when serialized to
transmit over the network. Specifying the ?human flag displays the
compressed size in a more human friendly manner. Note that even if the
cluster state request filters items from the cluster state (so a subset
of the cluster state is returned), the size that is returned is the
compressed size of the entire cluster state.
Closes#3415
577d2a6a1d