* (db/snapshot): Add LSN in Resource
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): add AddStepWithLsn
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): Add Lsn related logic
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): add operator << for Operation
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): fix lint errors
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): add more test
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): operation rollback api placeholder
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): remove hard code status code
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): support more printable dump for some operations
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): add ToString for Context
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): more friendly context print
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>

* (db/snapshot): rename some apis
Signed-off-by: Npeng.xu <peng.xu@zilliz.com>