fixes collection_command_simple call and streams in pooled mode

[elbywan]

Issue

• collection_command_simple call

It seems that the collection.cr command_simple function calls the LibMongoC.collection_command_simple binding with a missing argument.

In lib/mongo/src/mongo/collection.cr:63:18

 63 | if LibMongoC.collection_command_simple(self, command.to_bson, out reply, out error)
                   ^------------------------
Error: wrong number of arguments for 'LibMongoC#collection_command_simple' (given 4, expected 5)

• streams in pooled mode

Custom streams using a TCPSocket were not connecting to the db properly when in pooled mode, since polling is dedicated to a background thread unlike in single thread mode.

Done

• Added the mongo preferences prefs as a third argument to satisfy the call.
• Fixes socket connection when in pooled mode by adding a connected bool as a class variable and forcing connection when requesting the socket and connected is false.