Add support for C_GetInterfaceList

[frankmorgner]

In the OpenSC PKCS#11 module we are offering ABIs for both, version 2.4 and version 3.0. We're implementing this via C_GetInterface. Accessing C_GetFunctionList or C_GetInterface is not supported by rust-cryptoki, which currently only allows access to the default interface via C_GetFunctionList (i.e. the version 2.4 variant).

Please add wrappers for C_GetInterface to allow accessing all interfaces (i.e. version 3.0 as well for OpenSC).