[Dubbo-4351]Fix getRemoteApplicationName() returns null #4351

[CrazyHZM]

What is the purpose of the change

Fix RpcContext.getContext().getRemoteApplicationName() returns null #4351

In addition to jsonrpc, xmlrpc, webservice, thrift, others support RpcContext.getContext().getRemoteApplicationName().

Because jsonrpc, xmlrpc, webservice ,thrift do not support attachment.

Jsonrpc supports attachment I have done this in #4596, please review.

Brief changelog

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Verifying this change

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[cvictory]

@CrazyHZM There are some conflict in this pr

[CrazyHZM]

@CrazyHZM There are some conflict in this pr

Done.

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[beiwei30]

LGTM.