drivers: serial: stm32: Make it compatible with runtime PM on console

Since #53979, runtime PM can be applied on serial device used by console.
While it should be transparent on serial driver side as the application
(console in this case) is driving the PM runtime requests, on STM32
it requires some modification on serial driver as UART interrupts are
generated to handle internal power management house cleaning.
When these interrupts are generated, PM runtime should also be driven
to ensure clock availability when treating the uart ISR.
On STM32, some additional changes are required

Signed-off-by: Erwan Gouriou <erwan.gouriou@st.com>