fix: sql schema hardcoded in method query_get_table_metadata

[Ryuk-me]

Describe the bug
Description of what the bug is.

Database schema name is hardcoded as public in method query_get_table_metadata , when trying to fetch datasets/tables name from some other schema it still fetch public schema datasets

https://github.com/datachecks/datachecks/blob/main/datachecks/core/datasource/sql_datasource.py#L82

Expected behavior
It should be fetched from schema defined in datasource connection properties, if it is None/null then it should be some default value

To Reproduce
Use PostgreSQL
Create schema called second, Try to fetch table names using method query_get_table_metadata it fetches table names from the public schema

[Ryuk-me]

Fixed with #213