drivers: timer: Add ULPT timer for power management on Renesas RA MCUs

drivers:
- Added ULPT timer driver in `renesas_ra_ulpt_timer.c`.
- Updated `clock_control_renesas_ra_cgc.c` for ULPT clock settings.
- Updated `uart_renesas_ra8_sci_b.c` for power management support.
- Updated `CMakeLists.txt` and `Kconfig` to integrate ULPT timer.
- Added `Kconfig.renesas_ra_ulpt` for ULPT-specific configurations.

dts bindings:
- Added `renesas,ra-ulpt.yaml` for ULPT node bindings.
- Added `renesas,ra-ulpt-timer.yaml` for ULPT timer bindings.

modules:
- Updated `Kconfig.renesas_fsp` to support ULPT and LPM.

Signed-off-by: Khanh Nguyen <khanh.nguyen.wz@bp.renesas.com>

modules/Kconfig.renesas_fsp

@@ -169,6 +169,18 @@ config USE_RA_FSP_WDT
 	help
 	  Enable RA FSP WDT driver
 
+config USE_RA_FSP_ULPT
+	bool
+	help
+	  Enable RA FSP ULPT driver
+
+config USE_RA_FSP_LPM
+	bool
+	default y
+	depends on PM
+	help
+	  Enable RA FSP LPM driver
+
 endif # HAS_RENESAS_RA_FSP
 
 if HAS_RENESAS_RZ_FSP