[New Extension]: pg_qualstats

### Is there an existing issue for this extension request?

- [x] I have searched for an existing issue, and could not find a duplicate request.

### Extension Name

pg_qualstats

### Project Repository URL

https://github.com/powa-team/pg_qualstats

### Extension Website URL (Optional)

https://github.com/powa-team/pg_qualstats

### Short Description

pg_qualstats is a PostgreSQL extension that collects statistics on query predicates (WHERE clauses and JOIN conditions). It records execution counts and selectivity information per operator and column, enabling query tuning and index recommendation tools like PoWA.

### Main LICENSE Link

https://github.com/powa-team/pg_qualstats/blob/master/LICENSE

### License Compliance

- [x] The extension's license (linked above) complies with the list of allowed licenses.

### Known Dependent Extensions

None

### Component Owner and Maintenance Commitment

- [x] I/My organization commit to becoming the Component Owner and maintaining the extension image in the future.

### Additional Notes (Optional)

A PR implementing this extension is already open: #160

### GitHub Handles of Component Owners

@egkristi

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct