TPC-H q7, q8, q9 run failed when using String for Date

[weiting-chen]

Describe the bug
q7: error: invalid static_cast from type ‘std::string’ {aka ‘std::__cxx11::basic_string’} to type ‘int64_t’ {aka ‘long int’}
182 | castDATE_nullsafe_18 = static_cast<int64_t>(sort_merge_join_0_output_col_3);

q8: error: invalid static_cast from type ‘std::string’ {aka ‘std::__cxx11::basic_string’} to type ‘int64_t’ {aka ‘long int’}
199 | castDATE_nullsafe_4 = static_cast<int64_t>(sort_merge_join_0_output_col_3);
|
compilation failed,

q9: error: invalid static_cast from type ‘std::string’ {aka ‘std::__cxx11::basic_string’} to type ‘int64_t’ {aka ‘long int’}
149 | castDATE_nullsafe_4 = static_cast<int64_t>(sort_merge_join_0_output_col_5);
| ^
compilation failed,

To Reproduce

1. Set to use String for Date when generating data for TPC-H
2. Run TPC-H q7, q8, q9 will reproduce this issue.

Expected behavior
We expect to run pass q7, q8, q9 without any issues.