migrating commits from booting repo

The following merge requests in booting repo have been lost during migration to EF:

• https://booting.oniroproject.org/distro/meta-oniro-blueprints-core/-/merge_requests/1
• https://booting.oniroproject.org/distro/meta-oniro-blueprints-core/-/merge_requests/2

The commits that currently are missing in this repo and are being ported over are:

• connectivity: fix override syntax
• openthread: add 2001::/64 prefix to provide global unicast address
• ot-br-posix: add udev rule to ensure consistent rcp device naming
• ot-br-posix: make use of the stable rcp device name

Reporting here the content of the two merge requests:

ot-br-posix: add udev rule to ensure consistent rcp device naming

The RCP device shows up as USB ACM device. Depending on plug in order,
or a device USB reset this devioce name is not always defined to be
ttyACM0.

This udev rules helps us to keep the device name stable with a symlink
that links back to the original ttyACM? device. For now we support two
types of RCP devies in there (the only ones we have been working with in
Oniro). An OpenThread bare metal firmware flashed on the Makerdiary USB
dongle and the Zephyr + OpenThread based RCP firmware on the Arduino
Nano 33 BLE.

Signed-off-by: Stefan Schmidt <stefan.schmidt@huawei.com>

connectivity: fix override syntax and add change otbr configuration

## connectivity: fix override syntax

fix syntax according to kirkstone override syntax

## openthread: add 2001::/64 prefix to provide global unicast address

add 2001::/64 prefix to provide global unicast address to Thread interface. 
This allows Thread interface to be identified on a global scope, beyond a Thread network. 

This is needed for the coap communication to be established via OpenThread

Signed-off-by: Francesco Pham <francesco.pham@huawei.com>

Signed-off-by: Francesco Pham francesco.pham@huawei.com