fix Cursor to catch $err, even if not the first doc

$err can occur in OP_GET_MORE results, so we have to check for it
in every document.

Possibly, in the future, we can check just the first result of any
OP_GET_MORE, but that's non-trivial right now the way results are
retrieved in "has_next" but $err is checked in "next".
add private _batch_size attribute to Cursor

This allows testing max_time_ms.  In the future, it needs to be
rationalized with aggregate batch size so we can provide a single
batch size parameter to end users.
validate argument to max_time_ms
make bulk insert shallow copy document
add enableTestCommands to local orchestration server start
add max_time_ms.t file for maxTimeMS tests
skip maxTimeMS tests on mongos
add sharded+RS example to local orchstration config