include boilerplate for logging adapter version to database

There's a common pattern in adapters wherein the version is sent to a `user_agent_string` or `application_name` field when opening a connection that enables the underlying database's product team to have telemetry on the volume of dbt invocations that they're getting. This is normally found in the AdapterConnectionManager.open() method (e.g. [DatabricksConnectionManager.open()](https://github.com/databricks/dbt-databricks/blob/ae9df50807a5a9800e941eb1776eb6f72901742b/dbt/adapters/databricks/connections.py#L251-L263) )

If possible, it would be great to provide at least a template for adapter developers know that it's a good idea to do. Perhaps it can be mentioned in our how to guides in conjunction with `unique_field()`, which is used for dbt Labs's telemetry

https://github.com/dbt-labs/dbt-database-adapter-scaffold/blob/614506914bc5add23baa8b7a36aa906976804475/%7B%7Bcookiecutter.project_name%7D%7D/dbt/adapters/%7B%7Bcookiecutter.directory_name%7D%7D/connections.py#L89-L95