Add support for ConnInfo

[jsnb-devoted]

Is your feature request related to a problem? Please describe.
We are developing an app that uses ConnInfo method in pgx (link). We have our own interface for mocking but we want to move to pgxmock the issue I'm running into now is that our interface isn't compatible because the pgxIface is missing the ConnInfo method:

cannot use mock (variable of type pgxmock.PgxConnIface) as DBConn value in argument to getAllTables: pgxmock.PgxConnIface does not implement DBConn (missing method ConnInfo)

Describe the solution you'd like
Add the ConnInfo method to the interface if that is sensible/backwards compatible.

Describe alternatives you've considered
We are effectively doing the alternative by having our own interface but we are missing all the great unit testing functionality in pgxmock that we would like to use.

Additional context
I'll submit a naive PR for this. I suspect adding this could cause issues for current users of the package. I'm newer to go package development.