Roadmap after psycopg3 release

### Is your feature request related to a problem?

With the release of psycopg3 and its async capabilities, isn't this wrapper for the good-old synchronous psycopg2 unnecessary anymore?

### Describe the solution you'd like

At least I'd expect aiopg to mention its relation with psycopg3 and maybe declare sunset?

### Describe alternatives you've considered

During the timespan where other libraries that could rely on aiopg won't yet move to psycopg3, maybe aiopg2 should become a thin wrapper for psycopg3? E.g. SQLAlchemy won't support psycopg3 until their 2.0 release https://github.com/sqlalchemy/sqlalchemy/milestone/88

### Additional context

_No response_

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