driver: timer: Support for RX system timer

This commit add a system timer driver for Renesas RX using the
CMT peripheral. The driver supports both system ticks and
high-resolution cycle counting
- Configures CMT0 as the system tick timer
- Configures CMT1 as a free-running cycle timer for precise
  time tracking
- Handles timer overflows to maintain a continuous cycle count.
- Implements sys_clock_cycle_get_32() and sys_clock_cycle_get_64()
  for  high-resolution timing
- Supports Zephyr tickless kernel mode by tracking elapsed cycles
- Enables interrupt-based tick announcement using CMT0

Signed-off-by: Duy Nguyen <duy.nguyen.xa@renesas.com>
Signed-off-by: Yuichi Nakada <yuichi.nakada.sx@renesas.com>