Integrate Java DPG in sdk automation pipeline

[dw511214992]

doc: https://github.com/Azure/azure-rest-api-specs/tree/dpg-doc/documentation/onboard-dpg-in-sdkautomation

[weidongxu-microsoft]

existing package openapi-env-test/azure-rest-api-specs#3144
new package openapi-env-test/azure-rest-api-specs#3152

multi package with autorestConfig override openapi-env-test/azure-rest-api-specs#3148

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Behavior is different based on whether the SDK is already exists in SDK repo.

If SDK exists, automation takes the autorestConfig or the swagger/README.md (this implies SDK is approved by archboard, and user already knows how the configure works, then it is up to user to provide a correct configure), and completely rely on them.

If SDK does not exist, automation provides additional default settings, including data-plane, namespace, generate-samples, generate-tests etc. for user who is not familiar with autorest configuration.
And automation generates other auxiliary files like pom.xml, ci.yml, README.md, CHANGELOG.md, etc.