[libc] Add `IN6_IS_ADDR_MC*` (#172643)

This patch adds the `IN6_IS_ADDR_MC*` macro, which checks whether an
address is multicast node-local address, multicast link-local address,
multicast site-local address, multicast organization-local address and
multicast global address.

GitOrigin-RevId: 12d4889a0aa5ff816db818ca43f2bbb71610a0b2