Support r2dbc-spi's extension(optional) interface 'Wrapped'

[jchrys]

The Wrapped interface is an optional extension provided by the R2DBC specification to
access an instance of a resource which has been wrapped and for implementers to expose wrapped resources.

By implementing the Wrapped interface, vendors can expose their vendor-specific resources in a standard way.

This feature is not mandatory to implement, but we would like to add support for it in our implementation.

Refer to the R2DBC specification for more details: https://r2dbc.io/spec/1.0.0.RELEASE/spec/html/#wrapped.