:use_error_serialization_v2 config option isn't respected when using a custom Temporal::Configuration

[davehughes]

This was causing me some confusion and I tracked it down to this line, which uses the global singleton Temporal.configuration rather than the specific configuration that was used to create the connection.

I'm working on a PR to fix that:

1. adds use_error_serialization_v2 to the set of options respected by Temporal::Connection::GRPC.
2. plumbs this value through from Temporal::Configuration#for_connection which is used when actually creating the connection object in Temporal::Client#connection.