CodeGen from PR 13874 in Azure/azure-rest-api-specs

[Hub Generated] Review request for Microsoft.Synapse to add version preview/2021-04-01-preview (#13874)

* Adds base for updating Microsoft.Synapse from version stable/2021-03-01 to version 2021-04-01-preview

* Updates readme

* Updates API version in new specs and examples

* add changed files for kustoPool

* Ravi changes to fix LinDiff validation

* Add Itay Sofer's changes

* filizt comments mid-way

* Remove clouderror and resplace with "../../../../../common-types/resource-management/v2/types.json#/definitions/ErrorResponse"

* Add IotHubDataConnection and EventGridDataConnection

* Modify PUT to OK, CREATED, ACCEPTED

* Change from provisioningState to ResourceProvisioningState

* Add BlobStorageEventType

* Remove 202 when creating a KustoPool

* Change PUT/PATCH 202 responses

* Remove 202 in PATCH/PUT operations where having both 200 & 201

* Add "isIdentityCertExprired" to custom-words.txt

* Remove isIdentityCertExprired from custom-words.txt

* Add Exprired to cSpell.json

Co-authored-by: Amit Elran <amelran@microsoft.com>