Fix handling of unknown column types

[looi]

• Do only one thing
• Non breaking API changes
• Tested

What did this pull request do?

When using the go clickhouse driver, scanning into sql.RawBytes is not supported for most columns. I think the database/sql standard only guarantees that all columns can be converted to *interface{}, not RawBytes, so gorm should not make this assumption.

This issue doesn't affect most drivers like sqlite, mysql, postgres, but it does affect clickhouse. The following test will pass once this change is merged: go-gorm/clickhouse#128

User Case Description

[jinzhu]

This might broken query with maps?

If it is possible to make the clickhouse driver support sql.RawBytes, I think this might be a better solution?

[looi]

Why should it break maps? I think any driver would be happy to scan a map into interface{}?

I don't think changing the clickhouse driver is the right solution because the clickhouse driver isn't violating the spec. Even if the clickhouse driver is changed, gorm may still be broken with other compliant drivers.