strongswan: add eap-dynamic plugin

strongswan: add eap-dynamic plugin

This plugin acts as a proxy that dynamically selects an EAP method that is
supported/preferred by the client. If the original EAP method initiated by
the plugin is rejected with an EAP-NAK message, it will select a different
method that is supported/requested by the client.

For example it is possible to configure eap-tls as preferred
authentication method for your connection while still allow eap-mschapv2.

Signed-off-by: Tarvi Pillessaar <redacted>