refactor: optimize the memory consumption in tsdbread

fix: handle both null tag values

enh: add wal options to db

fix: set null when all inputs are null for leastsquare function

test: valgrind case

enh(query): add selectivity for output n-1 indifinite_rows function(diff & derivative)

refactor(sync): add pre-commit interface

doc: table, stable, database in sql manual

Enhanced crash_gen tool to report better error for deadlocks

test: valgrind case

feat(stream): refector some log