Find out all the deprecated things in our SDK and try using @deprecated attribute, see if it looks good.

Currently, at least for ApplicationContext, we've done deprecated via @note, and I think it is not noticeable enough, for something that is deprecated, see https://azuresdkdocs.blob.core.windows.net/$web/cpp/azure-core/1.14.0-beta.1/class_azure_1_1_core_1_1_context.html (and also we shoud drop ":" after @note there).