network: address: use usec_t for handling lifetime

network: address: use usec_t for handling lifetime

This drops stuct ifa_cacheinfo from Address, and store lifetime with
usec_t.

Why? Now, all requests of address configurations are once stored in
the request queue, and will be processed when it is ready. So, the
timestamp value passed to the kernel must be evaluated on configure.

This also fixes the following two issues.
- Time values in struct ifa_cacheinfo are stored in uint32_t.
  So, the validity check of the address configured by NDisc may fail on
  long running systems.
- If a system uses DHCPv6PD, when an interface may appear or be
  reconfigured later, then the lifetime value may be inappropriate.
  We need to adjust the lifetime with the current time and the timestamp
  of the lease.