refactor: adapt moonbit 0.9.3

[Yoorkin]

Summary

• Update deprecated MoonBit 0.9.3 APIs from Ref::new(...) to Ref(...) and empty Map::new() to Map([]).
• Migrate parser diagnostic failure messages from deprecated Show output to Debug output via to_repr(...), and derive Debug for Report.
• Use core/test's assert_eq in syntax white-box tests and import it for wbtest to avoid the deprecated Show-based assertion path.

Tests

• moon check
• moon test handrolled_parser
• moon test syntax
• moon test pkg_parser
• moon test test/sync_test
• moon fmt
• moon info