test(contrib/drivers/mysql): enhance data type tests (gogf#4705)

## Summary
- Add comprehensive tests for various data types (int, float, string,
[]byte, time, etc.)
- Add struct field type conversion tests
- Add JSON/XML data type tests
- Add binary data handling tests

**Test coverage added:** ~28 test functions

Ref gogf#4689

## Test plan
```bash
cd contrib/drivers/mysql
go test -v -run "TestModel_.*Type|TestModel_.*Convert"
```

Author: lingcoder