CodeGen from PR 14286 in Azure/azure-rest-api-specs

Anf 12288 [NetAppFiles] Add preview api version 2021-04-01-preview (#14286)

* Add folder for 2021-04-01-preview

* Add changes for 2021-04-01-preview

* pretty

* Update api-version in examples

* Update readme

* Update readme2

* Update folder name

* Rename folder

* Example ref

* Change enum name

* Change go preview folder

* Apply 2021-02-01 updates

* Update readme

* Update go readme

* update storageToNetworkProximity values

* Fix enum type

* Pretty

Co-authored-by: Audunn Baldvinsson <audunn.baldvinsson@netapp.com>