Allow New-AzSqlDatabaseImport to create a vCore-based database

Currently, New-AzSqlDatabaseImport accepts -Edition and -ServiceObjectiveName , which allow you to create a DTU-based SQL Database. However, I want to create a vCore-based SQL Database.

I'd like to see new optional parameters added.
* -Edition would be the General Purpose/Business Critical/Hyperscale tier
* -Vcore would be the number of vCores assigned
* -ComputeGeneration would be Gen5, F-Series, etc.

This is in line with the parameters for [New-AzSqlDatabase](https://docs.microsoft.com/en-us/powershell/module/az.sql/new-azsqldatabase?view=azps-4.6.0).

This is the code I'd like to run:

`New-AzSqlDatabaseImport `
` -DatabaseName $SQLDB `
` -Edition $DBEdition `
` -Vcore $Vcore `
` -ComputeGeneration $Gen `
` -DatabaseMaxSizeBytes $DBSize `
` -ServerName $SqlServerName `
` -StorageKeyType 'StorageAccessKey' `
` -StorageKey $StorageAcctKey `
` -StorageUri $StorageUri `
` -AdministratorLogin $SqlAdminUser `
` -AdministratorLoginPassword $SqlAdminPass `
` -ResourceGroupName $RGName `

Start at the New-AzSqlDatabaseImport entry point and compare its parameters with New-AzSqlDatabase, especially Edition, Vcore, and ComputeGeneration. Trace the existing DTU-based import path and its tests; done means the vCore-based example in the issue is accepted and covered by the repository's tests.

Written by the indexing model from the issue text.