[FEATURE][ODBC] Support SIGV4 along with Basic Auth

Is your feature request related to a problem?
Currently there are three auth types in ODBC driver: basic, sigv4, none.
Users can provide their FGAC credentials (username and password) using basic auth, and sigv4 will read opensearchodbc aws profile which contains IAM credentials.

There is a domain that uses both types of authentication. opensearch.log shows 401 authn error for basic and none auth types, and 403 authz error for sigv4 auth type. Looks like sigv4 got passed the aws validation, but since there were no username and password send, it did not go through the FGAC validation.

Feel free to edit/comment if the above assumption is wrong.

What solution would you like?
Provide an option in ODBC driver to allow user use their aws credentials with basic auth (username and password).

What alternatives have you considered?
A clear and concise description of any alternative solutions or features you've considered.

Do you have any additional context?
Add any other context or screenshots about the feature request here.

No files, tests, or entry points are named. Begin by locating the ODBC driver's basic, SigV4, and none authentication handling, then clarify how AWS credentials should combine with username and password; done means the selected behavior works for the affected domain and is covered by tests.