Support azure-json in azure-core-management

[alzimmermsft]

Description

Serializable model types in azure-core-management now implement JsonSerializable to support azure-json.

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• [x] The pull request does not introduce [breaking changes]
• [x] CHANGELOG is updated for new features, bug fixes or other significant changes.
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[azure-sdk]

API change check

APIView has identified API level changes in this PR and created following API reviews.

com.azure:azure-core com.azure:azure-core-management

[alzimmermsft]

@weidongxu-microsoft, it looks this PR may require a code generation update to resource manager libraries alongside with the changes made.

[weidongxu-microsoft]

@weidongxu-microsoft, it looks this PR may require a code generation update to resource manager libraries alongside with the changes made.

Yes, some change would affect / get affected by codegen change. E.g. for Resource we may want a protected ctor, or 3 protected setter (the choice would interfere with codegen when it generates the subclass of Resource -- so far mgmt does not use ctor with required parameters).

I am OK with current code though. It does not add protected API so far, so we can delay the change till we design codegen.