Azure Cosmos DB for PostgreSQL Cluster not showing in Azure Resources list

[alexweininger]

Copied over from microsoft/vscode-azureresourcegroups#1069 (@weissseaofsky)

---

Request: Add section for "Azure Cosmos DB for PostgreSQL Cluster" in resources list

*"PostgreSQL servers (Flexible)" only shows "Azure Database for PostgreSQL servers" resources.
*It doesn't show in "PostgreSQL servers (Standard)" or "Azure Cosmos DB" either: