[release-1.26] Enable external registry support for OCP e2e tests in CI

[istio-testing]

Manual cherrypick required.

#1514 failed to apply on top of branch "release-1.26":

Applying: Enable external registry support for OCP e2e tests in CI
Using index info to reconstruct a base tree...
M	tests/e2e/common-operator-integ-suite.sh
M	tests/e2e/setup/build-and-push-operator.sh
Falling back to patching base and 3-way merge...
Auto-merging tests/e2e/setup/build-and-push-operator.sh
CONFLICT (content): Merge conflict in tests/e2e/setup/build-and-push-operator.sh
Auto-merging tests/e2e/common-operator-integ-suite.sh
CONFLICT (content): Merge conflict in tests/e2e/common-operator-integ-suite.sh
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0001 Enable external registry support for OCP e2e tests in CI