[ovhcloud] openstack application credentials, gpu flavors update, stressed downscale fix

[mxm-tr]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This PR edits the ovhcloud provider with the following latest updates:

• Refactor ovh sdk.NodePool state cache to avoid store out-of-date copy of TargetSize, etc... that was leading to inconsistencies in few downscale cases. A pointer is used instead of copy when refreshing objects.

• Add another authentication method for the ovhcloud api, using Openstack application credentials.

• Update the GPU flavor prefix to match the current flavors on ovhcloud

Special notes for your reviewer:

This PR doesn't include any breaking change

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: mxm-tr / name: mxmtr (2c98b88, 3e037eb, fd485f9)

[k8s-ci-robot]

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: mxm-tr
Once this PR has been reviewed and has the lgtm label, please assign aleksandra-malinowska for approval. For more information see the Code Review Process.

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[mxm-tr]

/easycla