* [SaveData] Implement save data memory2 exports
Astro Bot calls sceSaveDataSetupSaveDataMemory2 during boot and asserts
and null-writes when it fails, so the missing import surfaces as a
named crash. This implements setup plus the companion get, set, and
sync operations that make it useful. The store is one zero-filled file
per user and title at sce_sdmemory/memory.dat under the save root,
readiness is the backing file's existence, and get, set, and sync
return MEMORY_NOT_READY before setup. Struct offsets follow the
publicly documented homebrew savedata headers.
* [SaveData] Write setup result before mutating the memory backing file
samto6