* Update nrf-pac to version that modifies nrf52 register layout to match
  nrf54 to reduce the amount of cfg needed for nrf54 support.
* Make the following peripherals available on nrf54: twim, twis, spim,
  spis, uart, buffered uarte, dppi, gpiote, pwm, saadc
* Add examples tested on the nrf54 dk

Some code is based on or copied from other pull requests, modified to match the new
nrf-pac layout.

Co-authored-by: Dmitry Tarnyagin <dt@jetro.no>

This change modifies UART initialization throughout Embassy to take pins
before interrupts.

Related to #1304.