net.box: add stream support to net.box

Add stream support to `net.box`. In "net.box", stream
is an object over connection that has the same methods,
but all requests from it sends with non-zero stream ID.
Since there can be a lot of streams, we do not copy the
spaces from the connection to the stream immediately when
creating a stream, but do it only when we first access space.
Also, when updating the schema, we update the spaces in lazy
mode: each stream has it's own schema_version, when there is
some access to stream space we compare stream schema_version
and connection schema_version and if they are different update
clear stream space cache and wrap space that is being accessed
to stream cache.

Part of #5860

@TarantoolBot document
Title: stream support was added to net.box
In "net.box", stream is an object over connection that
has the same methods, but all requests from it sends
with non-zero stream ID. Stream ID is generated on the
client automatically. Simple example of stream creation
using net.box:
```lua
stream = conn:new_stream()
-- all connection methods are valid, but send requests
-- with non zero stream_id.
```