Add cfg fun (#1501)

* save work

Signed-off-by: lichengming <chengming.li@zilliz.com>

* wal config&gtest

Signed-off-by: lichengming <chengming.li@zilliz.com>

* fix dco and lint error

Signed-off-by: lichengming <chengming.li@zilliz.com>

* try to fix lint error

Signed-off-by: lichengming <chengming.li@zilliz.com>

* try to fix clang-format issue

Signed-off-by: lichengming <chengming.li@zilliz.com>

* update change log

Signed-off-by: lichengming <chengming.li@zilliz.com>

* ajdjust the code by yudong's advice

Signed-off-by: lichengming <chengming.li@zilliz.com>

* fix error

Signed-off-by: lichengming <chengming.li@zilliz.com>

* recommit pr 1501,local gtest is ok

Signed-off-by: lichengming <chengming.li@zilliz.com>