dmctl: simplify default query-status output (#334)

[sre-bot]

cherry-pick #334 to release-1.0

---

What problem does this PR solve?

Current query-status command without any args in dmctl will print a lot of information but users are concerned about a little of them.

What is changed and how it works?

This PR generates and returns a simple task-list when users don't specify any arg. The proto files are not changed. This PR only generates task-list info in dmctl and modifies the output after receiving full dm-workers' info from dm-master.

The output will be like this format:

{
    "result": true,
    "msg: "",
    "tasks": [
        {
            "taskName": "task-1",
            "taskStatus": "Running",
            "workers": ["127.0.0.1:8262"]
        },
        {
            "taskName": "task-2",
            "taskStatus": "Error - Some error occurred in subtask",
            "workers": ["127.0.0.1:8262", "127.0.0.1:8263"]
        }
    ]
}

The status of a task is based on its subtasks. The definition is listed as follows:

Subtasks' status	Task's status
Any Paused and len(result.errors) > 0	Error - Some error occurred in subtask
Any Running and unit is "Sync" and relay is Paused/Stopped	Error - Relay status is Error/Paused/Stopped
Any Paused but without error	Paused
All New	New
All Finished	Finished
All Stopped	Stopped
Others	Running

Check List

Tests

• Unit test

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to be included in the release note

[codecov]

Codecov Report

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The diff coverage is 88.6363%.

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[csuzhangxc]

LGTM

[amyangfei]

LGTM