Synapse managed private endpoint support

Similar to Datafactory, when Synapse is provisioned with a Managed vNet it's recommended to have Managed Private Endpoints to resources it should communicate with. For Datafactory it's possible to do this with bicep ([link to docs](https://learn.microsoft.com/en-us/azure/templates/microsoft.datafactory/2018-06-01/factories/managedvirtualnetworks/managedprivateendpoints?pivots=deployment-language-bicep)), it would be great to have this for Synapse aswell

Compare the Data Factory managed private endpoint resource in the linked Bicep documentation with the corresponding Synapse ARM resource documentation. Then locate the existing Synapse type definitions and determine the schema needed for managed private endpoints; done means Synapse managed private endpoint resources can be represented in Bicep types.

Written by the indexing model from the issue text.