EAP server: Set per-EAP method session context

EAP server: Set per-EAP method session context

This can be used to limit TLS session resumption within a TLS library
implementation to apply only for the cases where the same EAP method is
used. While the EAP server method matching will be enforced separately
by EAP server method implementations, this additional steps can optimize
cases by falling back to full authentication instead of having to reject
attempts after having completed session resumption successfully.

Signed-off-by: Jouni Malinen <j@w1.fi>