Allow domain suffix match to be set in UI for EAP configurations

Add a "domain" field that allows the user to specify a domain
suffix match for an EAP network configuration. This field
will only be available when the user specifies a CA certificate for
an EAP-PEAP, EAP-TLS, or EAP-TTLS network. Under the hood, the
value entered into this field will be passed to WPA supplicant
as the |domain_suffix_match| configuration variable.

BUG: 25180141
Change-Id: Ib69b9519f475e90e40441ddff61c80be43cf624b
TEST: On angler, domain field appears for the EAP-PEAP, EAP-TLS
TEST: and EAP-TTLS networks.