{AzurePostgresql} fixes #22302 fix the regex for serverName property (#22355)

* {AzurePostgresql} fixes #22302 fix the regex for serverName property

fixes #22302 

PR to fix the regex for serverName property

As per [this](https://learn.microsoft.com/en-us/azure/postgresql/single-server/tutorial-design-database-using-azure-portal#create-an-azure-database-for-postgresql) docs, the Postgresql Server Name should have the below pattern:
-Server name must be at least 3 characters and at most 63 characters.
-Server name must only contain lowercase letters, numbers, and hyphens. The server name must not start or end in a hyphen.
-Server name must be available.

Current Regex is incorrect: `^[a-z][a-z0-9]*$` as it doesn't allow the hyphen. The correct Regex pattern should be `^[a-zA-Z0-9]+(-[a-zA-Z0-9]+)*`

* Update common-types.json

Author: navba-MSFT

specification/postgresql/resource-manager/Microsoft.DBforPostgreSQL/preview/2022-03-08-preview/common-types.json

@@ -13,7 +13,7 @@
       "required": true,
       "type": "string",
       "description": "The name of the server.",
-      "pattern": "^[a-z][a-z0-9]*$",
+      "pattern": "^[a-zA-Z0-9]+(-[a-zA-Z0-9]+)*",
       "minLength": 3,
       "maxLength": 63,
       "x-ms-parameter-location": "method"

specification/postgresql/resource-manager/types/common-types.json

@@ -13,7 +13,7 @@
       "required": true,
       "type": "string",
       "description": "The name of the server.",
-      "pattern": "^[a-z][a-z0-9]*$",
+      "pattern": "^[a-zA-Z0-9]+(-[a-zA-Z0-9]+)*",
       "minLength": 3,
       "maxLength": 63,
       "x-ms-parameter-location": "method"