fix: kstack initialized according to ld result

fix: sched needs to use task state;
fix: sscratch should be set according to task struct;
fix: set stvec to ktrap for ktask

feat: temp lock for puts

feat: can run on any single hart now

feat: cofigurable log serial output

blockbuf should contain key for construct/destruct;
feat: record dirty

feat: impl bcache with shared_lru

feat: impl reentrant lock