The changes of this PR for JdbcOracleClient are as follows:
#### bug fixes:
1. Fix the problem that if there is an approximate table name for Schema synchronization with a table name with `/` characters, the synchronization Column will be confused
2. Fix the NPE problem of metadata synchronization after enabling lower_case_table_names configuration
#### improvement:
1. Modify the method of synchronizing Oracle User to Doris Database mapping, use `metadata.getSchemas` instead of `SELECT DISTINCT OWNER FROM all_tables`
2. When synchronizing metadata, change `null` at the catalog level to `conn.getcatalog`
sort out the test cases of external table.
After modify, there are 2 directories:
1. `external_table_p0`: all p0 cases of external tables: hive, es, jdbc and tvf
2. `external_table_p2`: all p2 cases of external tables: hive, es, mysql, pg, iceberg and tvf
So that we can run it with one line command like:
```
sh run-regression-test.sh --run -d external_table_p0,external_table_p2
```
