refactor(task): move task out of runtime (#1845)

This is a pure refactor patch without any function changes.
The patch is aim to reduce the size and dependencies of task library,
mainly move the "task" out of "runtime", including:

- Add a test named "dsn_task_tests"
- Remove duplicate comments from **/CMakeLists.txt

.github/workflows/lint_and_test_cpp.yaml

@@ -167,6 +167,7 @@ jobs:
           - dsn.rep_tests.simple_kv
           - dsn_runtime_tests
           - dsn_security_tests
+          - dsn_task_tests
           - dsn_utils_tests
           - dsn.zookeeper.tests
           # TODO(yingchun): Disable it because we find it's too flaky, we will re-enable it after
@@ -251,6 +252,7 @@ jobs:
           - dsn.rep_tests.simple_kv
           - dsn_runtime_tests
           - dsn_security_tests
+          - dsn_task_tests
           - dsn_utils_tests
           - dsn.zookeeper.tests
           # TODO(yingchun): Disable it because we find it's too flaky, we will re-enable it after
@@ -340,6 +342,7 @@ jobs:
 #          - dsn.rep_tests.simple_kv
 #          - dsn_runtime_tests
 #          - dsn_security_tests
+#          - dsn_task_tests
 #          - dsn_utils_tests
 #          - dsn.zookeeper.tests
 #          - partition_split_test