test: add test case for tail , notice that this case only support sub table  and common table

fix(sync): send snapshot to multi nodes at the same time

fix: handle the memory leak of parser

fix(query): disable elapsed function split

fix: can't find docs

docs: move docs-en and docs-cn to docs

test: del some fulltest case

enh(query): add top/bottom function distributed split

feature: explain mulitway merge and merge interval optimization

refactor: adjust logs