Support multi-tenancy (OSOE-364)

[Piedone]

Currently, the Toolbox has some references to the Default site. If we want to test multi-tenancy, i.e. creating and launching tenants, then this needs to be extended.

• Update TenantTests too.
• Needs prefixing in GoToPageAsync() and in GoToRelativeUrlAsync().
• Needs refactoring of CreateAndEnterTenantAsync().
• Support multi-tenancy with SQL Server. The logic changing the SQL Server connection string in the appsettings.json file can be substituted with using the [Database Shells Configuration Provider](https://docs.orchardcore.net/en/latest/docs/reference/core/Shells/#database-shells-configuration-provider and changing all connection strings in a query.
• Support multi-tenancy with Azure Blob Storage. The logic in AzureBlobStorageManager can be changed to use a templated {{ ShellSettings.Name }} BasePath.
• Support multi-tenancy for snapshots.
• Refactor Lombiq.Hosting.Tenants.FeaturesGuard.Tests.UI.Extensions.TestCaseUITestContextExtensions.

[sarahelsaig]

The usage of "Default" could be replaced with UITestContext.TenantName which is already used by the TypedRoute. It's currently always set to "Default" and the user must manually change it, but it could be initialized using the way you described.