drivers: gpio: Implement pin interrupt enable and disable

Implement the driver method pin_interrupt_enable and pin_interrupt_disable.
This commit fixes getting the get_pending_int by updating the interrupts
field in the gpio_emul_data filed when interrupt is triggered. Also,
introduces a new filed enabled_interrupts to better simulate the
behavior of the interrupt pending and whether the interrupt is
enabled/disabled.

Signed-off-by: Sung-Chi Li <lschyi@google.com>