subtask of https://github.com/apache/incubator-hugegraph/issues/2265 - license header - [x] https://github.com/apache/incubator-hugegraph/pull/2446 - CI - [x] https://github.com/apache/incubator-hugegraph/pull/2480 - [x] https://github.com/apache/incubator-hugegraph/pull/2492 - to master - [x] https://github.com/apache/incubator-hugegraph/pull/2460 - [x] https://github.com/apache/incubator-hugegraph/pull/2498 - [x] https://github.com/apache/incubator-hugegraph/pull/2478 - [x] https://github.com/apache/incubator-hugegraph/pull/2528 - [x] https://github.com/apache/incubator-hugegraph/pull/2532 - [x] https://github.com/apache/incubator-hugegraph/pull/2536
subtask of #2265
Uselessannotation & refactor and mark the failed tests inhg-pd-test#2480pd-grpc,pd-common,pd-clientinto hugegraph #2460pd-grpc&pd-common&pd-client#2498pd-coreinto hugegraph #2478pd-serviceinto hugegraph #2528pd-distinto hugegraph & add core tests, client tests, and REST tests for PD #2532