test/integration: introduce robust harness and migrate BBR suite#1959

LukeAVanDrie wants to merge 3 commits intokubernetes-sigs:mainkubernetes-sigs/gateway-api-inference-extension:mainfrom

LukeAVanDrie:refactor/epp-hermetic-testsLukeAVanDrie/gateway-api-inference-extension:refactor/epp-hermetic-testsCopy head branch name to clipboard