Re-enable eap-{dynamic,peap} libcharon plugins

eap-dynamic might be quite useful for users because it allows clients to select an alternative EAP method if the one selected by the server initially is not supported.

eap-peap is still widely used by users because it is what most of the clients implement. It is often used in combination with EAP-MSCHAPv2 to authenticate e.g. WiFi clients (the TLS connection in EAP-PEAP protects the potentially weak password authentication in EAP-MSCHAPv2). For instance, using the same protocol for VPN clients allows reusing the existing AAA infrastructure (AD/RADIUS server).