Allow attaching a Cosmos DB Account with tenantId (without AccountKey)

[sevoku]

Attaching a Cosmos DB Account is currently only supported if the connections string contains an Account Key, however we do support Entra ID auth for attached accounts as well, hence the check should be removed.

This would also allow attaching accounts with localAuth disabled.

Limitation: for Entra ID we need an optional tenantId for Multi-Tenant support, otherwise VS Code won't be able to get the right token if the current principal is not part of the same tenant.

We should support a Connection String property TenantId and also add support for an additional tenantId parameter when opening external Urls, the tenant Id should then be stored with the workspace item.