soc: nxp: imxrt: add CONFIG_SECOND_CORE_MCUX_LAUNCHER

Add CONFIG_SECOND_CORE_MCUX_LAUNCHER. This Kconfig is only enabled when
using sysbuild targeting the Cortex-M4 core on the RT11xx series, and
results in loading a minimal application to the Cortex-M7 core that
boots the Cortex-M4 core. This makes developing on the M4 core simpler,
as the user can now simply target the core with sysbuild enabled and
flashing the application will work as expected.

Signed-off-by: Daniel DeGrasse <daniel@degrasse.com>