Add VarBinary column type

[billy1624]

PR Info

• Closes mismatched types; Rust type core::option::Option<alloc::string::String> (as SQL type VARCHAR) is not compatible with SQL type VARBINARY sea-orm#704

• Dependents:

  • MySQL VarBinary column type mapping sea-schema#67

Adds

• Add VarBinary column type as two out of three db backend support this datatype. Only SQLite doesn't support it

References

• https://mariadb.com/kb/en/varbinary/
• https://dev.mysql.com/doc/refman/8.0/en/binary-varbinary.html
• https://www.postgresql.org/docs/current/datatype-bit.html

[ikrivosheev]

@billy1624 thank you! LGTM!