CodeGen from PR 18882 in Azure/azure-rest-api-specs

Microsoft.DBForPostgreSQL/Flexible servers 2022-01-20-preview (#18882)

* Adds base for updating Microsoft.DBforPostgreSQL from version stable/2021-06-01 to version 2022-01-20-preview

* Updates readme

* Updates API version in new specs and examples

* 2022-01-20-preview onboarding.

* Updated as per comments.

* Fix the supported HA mode cross version breaking change

* Add "x-ms-identifiers"

* Fix XmsIdentifierValidation

* Added subscription and location properties for Delegated subnet usage.

* add missing type object .

* Fix prettier check and model validation errors.

* Fix for MissingTypeObject

Author: SDKAuto