[APIManagement] Update .NET SDK to new version 20210801 (#24886)

* new version client generation

* fix build error

* record test in new version

* add changelog

* update assembly and metadata

* fix code generation discrepency

* vnet and platform version tests (#7)

* add system data validation (#9)

* vnet and platform version tests

* validate system data

Co-authored-by: Kacie <35987382+KacieKK@users.noreply.github.com>

* backup restore using msi (#10)

* new changes

* bump version

* added test for private endpoint (#11)

* playback

* Update private endpoint test (#12)

* added test for private endpoint

* updated test

Co-authored-by: Kacie Kang <jikang@microsoft.com>
Co-authored-by: Samir Solanki <samirsolanki@outlook.com>
Co-authored-by: Alan Feng <15934598+yingru97@users.noreply.github.com>

eng/mgmt/mgmtmetadata/apimanagement_resource-manager.txt

@@ -3,12 +3,13 @@ AutoRest installed successfully.
 Commencing code generation
 Generating CSharp code
 Executing AutoRest command
-cmd.exe /c autorest.cmd https://github.com/Azure/azure-rest-api-specs/blob/master/specification/apimanagement/resource-manager/readme.md --csharp --version="2.0.4417" --reflect-api-versions --tag=package-2020-12 --csharp-sdks-folder=C:\azure-sdk-for-net\sdk
-2021-05-21 07:03:54 UTC
+cmd.exe /c autorest.cmd https://github.com/Azure/azure-rest-api-specs/blob/main/specification/apimanagement/resource-manager/readme.md --csharp --version="2.0.4417" --reflect-api-versions --tag=package-2021-08 --csharp-sdks-folder=C:\azure-sdk-for-net\sdk
+Autorest CSharp Version: 2.3.91
+2022-01-11 19:00:51 UTC
 Azure-rest-api-specs repository information
 GitHub fork: Azure
-Branch:      master
-Commit:      5047dfdf585969892ac035ffdfbc57623f0bf1c5
+Branch:      main
+Commit:      e1b38934a6e3bd0fcb22a7c8e0a8522957aa1d9b
 AutoRest information
 Requested version: v2
 Bootstrapper version:    autorest@2.0.4417

sdk/apimanagement/Microsoft.Azure.Management.ApiManagement/CHANGELOG.md

@@ -1,5 +1,13 @@
 ## Microsoft.Azure.Management.ApiManagment release notes
 
+### Changes in 8.0.0-preview
+
+- Switch the .NET client to use api-version `2021-08-01`
+- new entities added, are `Hostname Configuration`, `AccessType`, `CertificateSource`, `ConnectionStatus`, `HTTPHeader`, `IssueType`, `PlatformVersion`, `SystemData`.
+- Added support for `PrivateLink`.
+- Added support for OpenAPI info contact, license, TOS support.
+- Added List operations to get `OutboundNetworkDependenciesEndpoints`.
+
 ### Changes in 7.0.0-preview
 
 - Switch the .NET client to use api-version `2020-12-01`