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.
tos_mmheap_check: get the information of the heap(space that is free and used)
tos_mmheap_pool_check: get the information of a pool
TOS_CFG_MMHEAP_DEFAULT_POOL_EN: enable the default pool of the heap(if user not set this, a default of 1u is set). if you wanna disable the default pool, you should call tos_mmheap_pool_add to add your own pool of the heap before tos_mmheap_alloc is called.
