Remove SkipIntegrationTests in favor of Skip*IntegrationTests.

What does this MR do?

As an alternative to !2065 (merged):

• As suggested by @ggeorgiev_, rather than copying/pasting helpers.SkipIntegrationTests(t, "kubectl", "cluster-info") we instead use a helpers.SkipKubernetesTests(t) etc.
• Cache the result at test initialization rather than shell out multiple times.

Why was this MR needed?

It addresses #25553 (closed), is hopefully neater, and should speed up tests.

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

• Documentation created/updated
• Added tests for this feature/bug
• In case of conflicts with master - branch was rebased

What are the relevant issue numbers?

Closes #25553 (closed)

Closes !2065 (merged)