Enhance OCI AUTHENTICATION value parsing to be case-insensitive

[MouhsinElmajdouby]

Using AUTHENTICATION values with lowercase or mixed case in OCI configuration inputs currently fails with an Unrecognized value error, even when the value is otherwise valid(for example oci_default instead of OCI_DEFAULT). The same issue also applies to resource providers when using authenticationMethod values with different casing. This causes
parsing to fail early and blocks connection setup for users who provide different casing. For consistency, AUTHENTICATION and authenticationMethod values should be parsed case-insensitively, the same way parameter names are already handled case-insensitively.