Add IBM Cloud service endpoint override support (API)

User Story:

A user currently is not able to create a Disconnected cluster, using IPI, on IBM Cloud.

Currently, support for BYON and Private clusters does exist on IBM Cloud, but support to override IBM Cloud Service endpoints does not exist, which is required to allow for Disconnected support to function (reach IBM Cloud private endpoints).

Description:

IBM Cloud VPC (x86_64) currently does not support Disconnected cluster installation via IPI.

In order to add this support, the override of certain IBM Cloud Services (e.g., IAM, IaaS), must be configurable and made available in the cluster infrastructure resource.

Acceptance Criteria:

API changes must be merged and then pushed (updated) to the required repositories/components in order to gain access to these override endpoint options.