tests: kernel: also move the test_isr_dynamic to new ztest API

`test_isr_dynamic` for `CONFIG_GEN_SW_ISR_TABLE=n` was somehow
overlooked in commit b7f1e987.

I'm disabling the irq at the end of the test. The babblesim for the
`nrf5340bsim_*` target walked into a timeout otherwise.

Signed-off-by: Greter Raffael <rgreter@baumer.com>