KEP-3619: Graduate "Fine-grained SupplementalGroups control" To GA

[everpeace]

• One-line PR description: This PR updates KEP-3169 to reflect the graduation of the "Fine-grained SupplementalGroups control" feature to General Availability (GA), targeting the v1.35 release.

• Issue link: Fine-grained SupplementalGroups control #3619

• Other comments: This PR also includes
  • some cleanups in the KEP (adjusting GA criteria and other minor adjustments).
  • PRR approval request

/kind documentation
/sig node

/assign @thockin @mrunalp @SergeyKanzhelev @haircommander (as the KEP reviewers)
/assign @johnbelamaric (as PRR approver)

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[everpeace]

I updated GA criteria in two points:

• I removed "gVisor.." criteria because it is a low-level container runtime, which is not relevant to the feature. And two major CRI runtimes (containerd, CRI-O) already support this feature. I think it's enough to promote this feature to GA
• I removed conformance test criteria. IIUC, CRI runtime dependent features can't be added to the conformance test. So, I removed it.