Allow Google Cast to connect to Cast devices on all IP addresses.

Unless EnableMediaRouter is set to Disabled, setting MediaRouterCastAllowAllIPs to Enabled connects Google Cast to Cast devices on all IP addresses, not just RFC1918/RFC4193 private addresses. Setting the policy to Disabled connects Google Cast to Cast devices only on RFC1918/RFC4193. Leaving the policy unset connects Google Cast to Cast devices only on RFC1918/RFC4193, unless the CastAllowAllIPs feature is turned on.