Inconsistent Handling of Config ID in Benchmark Class

Hi Everyone,

the `config_id` is handled inconsistently in the `query` and `get_config` method. In the former it is converted into a string and in the latter it is not.

Please compare:

https://github.com/automl/LCBench/blob/17e63756b927cb814bad3275640f8be12639820a/api.py#L31-L39

versus

https://github.com/automl/LCBench/blob/17e63756b927cb814bad3275640f8be12639820a/api.py#L108-L112

Read api.py at lines 31-39 and 108-112, comparing how config_id is handled in query and get_config. Done means both methods handle config_id consistently, with the behavior checked against the issue's stated discrepancy.

Written by the indexing model from the issue text.