Support Private Gateway and Static Route

[btzq]

Cloudstack now allows regular users to create Private Gateways without root access.

However, this update hasn't been integrated into the Terraform provider. Would like to request that this be supported to reduce our manual efforts.

Additionally, support for Static Routes configurations, especially with user-created gateways, could enhance functionality.

[kiranchavala]

@btzq thanks for rasing the issue

We can consider this for future release

[kiranchavala]

Closing the issue as #180 solves it