stm32 LPTIM clock with prescaler to adjust the TICKS_PER_SEC

[FRASTM]

When the LPTIM is enabled for the lowPower (PM) purpose, the SYS_CLOCK_TICKS_PER_SEC is set to a lower value (than default 10000)

• 4000 if LPTIM is clocked by LSI (32000Hz)
• 4096 if LPTIM is clocked by LSE (32768Hz)

However when the lptim has a that divides the clock source , this SYS_CLOCK_TICKS_PER_SEC is even too high, resulting in numerous system wakeup during sleep mode (no more sleeping indeed)
Consequently the SYS_CLOCK_TICKS_PER_SEC is set to a value depending
on the clock input LSE/LSI and the clock prescaler property set in the DTS

• 1000 if LPTIM is clocked by LSI (32000Hz) divided by 32
• 1024 if LPTIM is clocked by LSE (32768Hz) divided by 32
• 2000 if LPTIM is clocked by LSI (32000Hz) divided by 16
• 2048 if LPTIM is clocked by LSE (32768Hz) divided by 16

Removing SYS_CLOCK_TICKS_PER_SEC in the board config and adding
Warning build message to check the coherency between

• clock source definition (LSI/LSE) and the board DTS (lptim node property)
• SYS_CLOCK_TICKS_PER_SEC and the LPTIM clock ratio (lptim node <st,prescaler> property)

Fixes #61099

[erwango]

I think this is a good occasion to remove the deprecation message on "#if DT_INST_NUM_CLOCKS(0) == 1
#warning Kconfig for LPTIM source clock (LSI/LSE) is deprecated, use device tree."

[FRASTM]

Rebase on 68365d5
Update the SYS_CLOCK_TICKS_PER_SEC in the soc/arm/st_stm32/common/Kconfig.defconfig.series
to retrieve the prescaler from the deviceTree.
Requires to define the lptim prescaler property as <clock-prescaler> (instead of "st,prescaler")
because it is not accepted by the macro but $(dt_node_int_prop_int,$(DT_STM32_LPTIM_PATH),clock-prescaler)
Add a generic name stm32_lp_tick_source to the lptim node (= the lptim enabled for low power tick counter)
a board overlay is now defining the prescaler with :

&stm32_lp_tick_source {
	clock-prescaler = <32>;
};

[FRASTM]

rebase on #65683 which removes the lptim clock source divider of the stm32u5

[FRASTM]

rebase on 9521371

[FRASTM]

• rebase on f46a27f
• add comment to soc/arm/st_stm32/common/Kconfig.defconfig.series
• update the /doc/releases/migration-guide-3.6.rst

[FRASTM]

adding more text to the README.rst