[nat64] configure nat64 prefix in Tayga

[xuyirio]

This commits configures nat64 prefix /etc/tayga.conf when starting border agent. Tayga is restarted after configuration.

The _nat64 script is also updated to be compatible with prefix configuration by otbr-agent.

OTBR_TAYGA_NAT64 & OTBR_ENABLE_TAYGA_NAT64 are defined to guard the enablement of configuration.

Tests will be updated in a following PR.

[codecov[bot]]

Codecov Report

Merging #1160 (c97ae47) into main (2b41187) will increase coverage by 0.17%. The diff coverage is n/a.

:exclamation: Current head c97ae47 differs from pull request most recent head 65bc764. Consider uploading reports for the commit 65bc764 to get more accurate results

@@            Coverage Diff             @@
##             main    #1160      +/-   ##
==========================================
+ Coverage   55.77%   55.95%   +0.17%     
==========================================
  Files          87       87              
  Lines        6890     6791      -99     
==========================================
- Hits         3843     3800      -43     
+ Misses       3047     2991      -56     

Impacted Files	Coverage Δ
src/border_agent/border_agent.cpp	82.60% <ø> (-1.64%)	:arrow_down:
src/utils/thread_helper.cpp	47.92% <0.00%> (-3.14%)	:arrow_down:
src/dbus/server/dbus_thread_object.cpp	20.82% <0.00%> (-0.46%)	:arrow_down:
src/dbus/client/thread_api_dbus.hpp	50.00% <0.00%> (ø)
src/mdns/mdns_mdnssd.cpp	20.69% <0.00%> (+0.07%)	:arrow_up:
src/ncp/ncp_openthread.cpp	71.87% <0.00%> (+0.11%)	:arrow_up:
tests/unit/test_pskc.cpp	22.58% <0.00%> (+0.70%)	:arrow_up:
src/agent/main.cpp	67.07% <0.00%> (+1.19%)	:arrow_up:
src/mdns/mdns_avahi.cpp	47.22% <0.00%> (+1.39%)	:arrow_up:
... and 1 more

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[xuyirio]

@simonlingoogle @wgtdkp @bukepo @zhanglongxia Could you help take another look at this PR? Although we are still evaluating 1) using Tayga and integrate with 1P products vs. 2) building a new stateful NAT64 service, I'd like to get the Tayga configured with the appropriate prefix first. This will help us create a prototype quickly and make testing easier. Thanks!

[simonlingoogle]

I'd like to get the Tayga configured with the appropriate prefix first. This will help us create a prototype quickly and make testing easier. Thanks!

+1. I think a TAYGA based approach can still be useful for open source solutions, at least in the short term.