boards: nordic: Align with updated Nordic owned memory bindings

Apply the following changes to `nrf54h20dk` and `nrf9280pdk`:

* Convert `perm-*` properties to the newly introduced `nordic,access`,
  both in board files and tests.

* Redefine shared regions to specify multiple access owners per node,
  and ensure that each such region is reserved by one domain at a time.
  `cpuapp_cpurad_ram0x_region` is only enabled by Radiocore, while
  `cpuapp_cpucell_ram0x_region` is only enabled by Application core.

* Divide `shared_ram3x_region` so that each sub-region is owned by a
  different domain. Their addresses must be rounded down to fit the
  current UICR format.

Signed-off-by: Grzegorz Swiderski <grzegorz.swiderski@nordicsemi.no>