Add Org VDC network support for NSX-T VDC Groups

[Didainius]

This PR works to add support for NSX-T VDC Groups in Org VDC networks (routed, isolated and imported).

It also adds a new type AnyTypeEdgeGateway and methods AdminOrg.GetAnyTypeEdgeGatewayById, Org.GetAnyTypeEdgeGatewayById, AnyTypeEdgeGateway.IsNsxt, AnyTypeEdgeGateway.GetNsxtEdgeGateway.

Type AnyTypeEdgeGateway uses the same structure OpenAPIEdgeGateway which NSX-T Cousin type uses, but AnyTypeEdgeGateway Get methods will retrieve both - NSX-T and NSX-V Edge gateways. This is required as a convenience functions of Org VDC network routed network (because it can be backed by NSX-T or NSX-V).

Also adds some additional convenience functions: and methods:

• VdcGroup.GetNsxtImportableSwitchByName (similar to Vdc.GetNsxtImportableSwitchByName)
• Org.GetOpenApiOrgVdcNetworkByNameAndOwnerId
• VdcGroup.GetOpenApiOrgVdcNetworkByName
• VdcGroup.GetAllOpenApiOrgVdcNetworks
• VdcGroup.GetCapabilities
• VdcGroup.IsNsxt

[Didainius]

Final ask, please update PR description with the new AnyType prefix too. Thank you for the refactoring!

Done