addr: Refactor is_local_addr() to support IPv6

Series of changes:

  1. Rename function to reflect the namespace of the file.

  2. Use the new last resolved cache instead of the unused
     last_resolved_addr_v4 (which is also removed in this commit).

  3. Make the entire code base use the new resolved_addr_is_local() function.

You will notice that this function uses /24 to differentiate subnets where the
rest of tor uses /16 (including documentation of EnforceDistinctSubnets).
Ticket #40009 has been opened for that.

But that the moment, the function keeps looking at /24.

Part of #33233

Signed-off-by: David Goulet <dgoulet@torproject.org>