add kv fs component

1. a true wear-leveling kv fs for norflash, especially optimize for some onchip norflash with "write once on one single write unit" like stm32l4, a true "no earse before write" flash algorithm.
2. an "as less as possible" gc strategy, do best to save norflash's life.
3. full "power down protection" support
4. see "examples" of kv, project in "TencentOS_tiny_EVB_MX_Plus", with onchip flash and qspiflash sample.

kernel/core/tos_task.c

@@ -547,7 +547,7 @@ __API__ k_task_t *tos_task_curr_task_get(void)
     return curr_task;
 }
 
-__API__ void tos_task_walkthru(k_task_walker walker)
+__API__ void tos_task_walkthru(k_task_walker_t walker)
 {
     TOS_CPU_CPSR_ALLOC();
     k_task_t *task;