[nat64] implement nat64 translator (ot::Nat64::Translator) (#7836)

This commit:

- implements the core logic for translating packets for NAT64,
  including the public APIs exposed to platform daemons.

- includes changes for POSIX platform, use `OT_POSIX_NAT64_CIDR`,
  `OPENTHREAD_POSIX_CONFIG_NAT64_CIDR` for setting the CIDR for NAT64
  during build time.

- exposes `otNat64Send(otInstance *aInstance, otMessage *aMessage)`
  and `void otNat64SetReceiveIp4Callback(otInstance *aInstance,
  otNat64ReceiveIp4Callback aCallback, void *aContext)`.

script/make-pretty

@@ -84,6 +84,7 @@ readonly OT_CLANG_TIDY_BUILD_OPTS=(
     '-DOT_BORDER_ROUTER=ON'
     '-DOT_BORDER_ROUTING=ON'
     '-DOT_BORDER_ROUTING_NAT64=ON'
+    '-DOT_NAT64_TRANSLATOR=ON'
     '-DOT_CHANNEL_MANAGER=ON'
     '-DOT_CHANNEL_MONITOR=ON'
     '-DOT_CHILD_SUPERVISION=ON'