Add computed columns support to System-versioned temporal tables

- SqlPackage or DacFx Version: Any
- .NET Framework (Windows-only) or .NET Core: Any
- Environment (local platform and source/target platforms):

**Steps to Reproduce:**

1. Create a temporal system versioning table with computed column
2. Try to deploy it.
3. You will see the "System-versioned temporal tables with computed columns are not supported." even though this is supported in SQL server.

**Did this occur in prior versions? If not - which version(s) did it work in?**

(DacFx/SqlPackage/SSMS/Azure Data Studio)

Start by reproducing the deployment described in the issue: create a SQL Server system-versioned temporal table with a computed column and deploy it. Trace the temporal-table validation that reports computed columns as unsupported, then verify that deployment succeeds for this schema without breaking existing temporal-table checks.

Written by the indexing model from the issue text.