Support transaction_name_groups and use_path_as_transaction_name

[stevejgordon]

I think it makes sense for us to implement transaction_name_groups.

As part of implementing this, we need to consider what our default should be for scenarios such as WCF where the ElasticApmModule should default to $method unknown route and also support: use_path_as_transaction_name to opt into this behavior. This would be a sensitive change to our existing behavior, though.