soc: st: stm32: reference counting for backup domain accesses

Add SoC functions to enable/disable STM32 backup Domain access
and use a reference counter to track requests. These helper functions
may be called from a interrupt context. On domain access enable, the
function loops until written bit is set however this is expected to be
effective after very few clock cycles and seems not even required
(not mentioned in any SoC documentation). The loop is preserved as
used in previous implementation.

Among all supported STM32 SoCs, only STM32C0 and STM32WB0 series do not
implement this mechanism hence add option CONFIG_STM32_BACKUP_PROTECTION
that is enabled for all SoC series but these 2.

Fixes issue 90942.

Signed-off-by: Etienne Carriere <etienne.carriere@foss.st.com>