etcd support mapping

[qyi71]

What is the purpose of the change

etcd support mapping

Brief changelog

Verifying this change

XXXXX

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[qyi71]

@songxiaosheng PTAL
ref:apache/dubbo#14337

[wcy666103]

The review can be referenced here #380

[qyi71]

The review can be referenced here #380

I have some doubts, what do I need to do ？，i need consistent with the 'registerServiceAppMapping' method? or close this pr