{Core} Add US Gov cloud endpoint for synapse (#15881)
{Core} Add US Gov cloud endpoint for synapse (#15881)

* {Docs} Remove stale reference in README to closed issue about extensions (#12771)

* Add endpoint and resource id for UsGov cloud, and change the resource id for mooncake

Co-authored-by: Daniel Miller <27ad6e741c5a2bb4c10b540fe1a9d163327702a7@gmail.com>
Co-authored-by: Azure CLI Team <f94f0f8f1115ee1e929353685a336eee53796507@microsoft.com>
Co-authored-by: Zhenyu Zhou <f2395a04d0b1b7a8fef4575ddfaf978c8e6baa84@microsoft.com>
yugangw-msft/azure-cli,yugangw-msft/azure-cli,yugangw-msft/azure-cli,yugangw-msft/azure-cli,yugangw-msft/azure-cli,yugangw-msft/azure-cli