drivers: intc: plic: implement irq affinity configuration

- Implement irq-set-affinity in RISCV PLIC.
- Added new affinity shell command to get/set the irq(s)
  affinity in runtime, when `0` is sent as the `local_irq`, it
  means set/get all IRQs affinity.
- Some minor optimizations

Updated the build_all test to build this new configuration.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>
Signed-off-by: Yong Cong Sin <yongcong.sin@gmail.com>