chore: test suite refactor

[lkingland]

This PR provides the general structure for an upgrade to the testing system (both integration and E2Es) relying on the newly created Host builder for core functionalit, along with general simplification.

Currently a WIP.

/kind cleanup

[knative-prow[bot]]

Skipping CI for Draft Pull Request. If you want CI signal for your change, please convert it to an actual PR. You can still manually trigger a test run with /test all

[knative-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: lkingland

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[knative-prow-robot]

PR needs rebase.

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[github-actions[bot]]

This Pull Request is stale because it has been open for 90 days with no activity. It will automatically close after 30 more days of inactivity. Reopen with /reopen. Mark as fresh by adding the comment /remove-lifecycle stale.