Update MODP groups for IKEv2/IPsec VPNs

This commit improves security by removing MODP groups that are
considered to be breakable in the near-future, and adding support for
ones that are more highly recommended.

3072 and 4096 are added based on the IANA constants, and are already
supported in the IKEv2 library.

This commit is made in line with recommendations in RFC 8247:
https://tools.ietf.org/html/rfc8247#section-2.4

Bug: 154056830
Test: FrameworksNetTests, FrameworksIkeTests passing, manually tested.
Change-Id: I941dbbfc2d6be693869ba6213590a07f3eac4bc7