OSD-25124: new WIFOnly flag on version gates

[Nikokolas3270]

This flag will be used to filter out version gates applying on OSD (managed) clusters running on GCP provider with WIF (Workload Identity Federation) enabled.

[Nikokolas3270]

After discussion:

• Multiplying the Only suffixed members is not the way to go. Indeed what if we have to support a similar scheme on azure in the future?
• It was proposed to eventually introduce an OIDCScheme member that would take its values in STS, WIF or the empty string... but doing so looks like labelling the version gate. So actually it may better to extend the use of the existing Label member. The label seems to be used for information purposes only for now. What about using it for filtering as well?