`GenericDialect` should support multi-table DELETE and DELETE without FROM clause

According to the design policy, `GenericDialect` is intended to parse any SQL that other dialects can handle, but it currently fails to parse multi-table DELETE statements and DELETE statements without a FROM clause.

I think the expected behavior is that the following tests should also pass with `GenericDialect`.

https://github.com/apache/datafusion-sqlparser-rs/blob/2182f7ea71242a7e9674932d559baef67dae522d/tests/sqlparser_common.rs#L688-L735

Start with tests/sqlparser_common.rs lines 688-735 and run the referenced tests using GenericDialect. Trace the parsing path for multi-table DELETE statements and DELETE statements without a FROM clause. Done means both existing test groups pass with GenericDialect.

Written by the indexing model from the issue text.