ci: enable gcp-sev-snp for daily tests

[daniel-weisse]

Context

gcp-sev-snp was disabled on daily e2e tests since we currently don't have stable images for this variant. However, we the test was disabled for both debug and stable images.

Proposed change(s)

• Enable gcp-sev-snp for daily test runs
  • Currently excludes stable images from the test
• Fix verify e2e test for gcp-sev-snp
  • Properly create the JSON file for gcp-sev-snp and upload it
  • Remove a check for backwards compatibility with old CLI versions (v2.13)
  • e2e test

Related issue

• Fixes https://github.com/edgelesssys/issues/issues/547

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