openthread-br: bump to 2025-06-12 and add patch for CMake >= 4.0 support

openthread-br: bump to 2025-06-12 and add patch for CMake >= 4.0 support

Bump to version 2025-06-12 and add pending patch for openthread-br for
CMake >= 4.0 support.

The package use an old cJSON version that cause compilation problem with
CMake >= 4.0 support. To handle this, add a pending patch to use an
external version of cJSON.

We already ship this package so it's trivial to use that instead of the
one in the openthread-br repository.

Signed-off-by: Christian Marangi <redacted>