doc: migration-guide-3.6: zbus related migrations

  respective ``reset-gpios``. This has been fixed so those signals now have to

  be flagged as :c:macro:`GPIO_ACTIVE_LOW` in the devicetree. (:github:`64800`)

* The :kconfig:option:`ZBUS_MSG_SUBSCRIBER_NET_BUF_DYNAMIC`

  and :kconfig:option:`ZBUS_MSG_SUBSCRIBER_NET_BUF_STATIC`

  zbus options are renamed. Instead, the new :kconfig:option:`ZBUS_MSG_SUBSCRIBER_BUF_ALLOC_DYNAMIC`

  and :kconfig:option:`ZBUS_MSG_SUBSCRIBER_BUF_ALLOC_STATIC` options should be used.

* The ``CONFIG_ZBUS_MSG_SUBSCRIBER_NET_BUF_DYNAMIC`` and

  ``CONFIG_ZBUS_MSG_SUBSCRIBER_NET_BUF_STATIC`` zbus options are renamed. Instead, the new

  :kconfig:option:`CONFIG_ZBUS_MSG_SUBSCRIBER_BUF_ALLOC_DYNAMIC` and

  :kconfig:option:`CONFIG_ZBUS_MSG_SUBSCRIBER_BUF_ALLOC_STATIC` options should be used.

  (:github:`65632`)

* To enable the zbus HLP priority boost, the developer must call the

  :c:func:`zbus_obs_attach_to_thread` inside the attaching thread. The observer will then assume the

  attached thread priority which will be used by zbus to calculate HLP priority. (:github:`63183`)

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