Add project-scoped API endpoints for OpenStack

[embik]

As part of kubermatic/kubermatic#7260, we need to provide KKP API endpoints that are "project-aware", e.g. from /v2/providers/gke/sizes to /v2/projects/{project_id}/providers/gke/sizes because those API endpoints can use Presets as credentials, and we need information about the project context to determine whether a project-scoped preset can be used or not.

Acceptance Criteria

• All provider-specific API endpoints for OpenStack gain a project-specific equivalent.