Export shared ko apply helper

[Minsoo Kim (33modeling)]

Summary

• export KoApply from the shared E2E package
• replace duplicated ko apply command setup in the sizing, egress authorization, and capabilities suites
• update existing internal callers to use the exported name

Fixes #1251

Testing

• env -u NO_COLOR go test ./internal/e2e ./internal/e2e/suites/sizing ./internal/e2e/suites/egressauthz ./internal/e2e/suites/capabilities
• git diff --check

AI disclosure

AI tools assisted with preparing this change. I reviewed the diff and ran the listed tests before submission.

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