arch: arm: cortex_m: Add config for SW_VECTOR_RELAY_CLIENT

Define vector relay tables for bootloader only.
If an image is not a bootloader image (such as an MCUboot image)
but it is a standard Zephyr firmware, chain-loadable by a
bootloader, then this image will not need to relay IRQs itself.
In this case SW_VECTOR_RELAY_CLIENT should be used to setting the
vector table pointer in RAM so the parent image can forward the
interrupts to it.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
Co-authored-by: Øyvind Rønningstad <oyvind.ronningstad@nordicsemi.no>
Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>