arch: arm: Add support for multiple zero-latency irq priorities

Add the ability to have multiple irq priority levels which are not
masked by irq_lock() by adding CONFIG_ZERO_LATENCY_LEVELS.

If CONFIG_ZERO_LATENCY_LEVELS is set to a value > 1 then multiple zero
latency irqs are reserved by the kernel (and not only one). The priority
of the zero-latency interrupt can be configured by IRQ_CONNECT.

To be backwards compatible the prio argument in IRQ_CONNECT is still
ignored and the target prio set to zero if CONFIG_ZERO_LATENCY_LEVELS
is 1 (default).

Implements #45276

Signed-off-by: Christoph Coenen <ccoenen@baumer.com>