feat(db/schema): do not allow setting priority with traditional route in mixed mode

[chronolaw]

Summary

Notice: regex_priority and priority have the default value 0, so we think 0 is equivalent to "not set".

KAG-4411

Checklist

• The Pull Request has tests
• A changelog file has been created under changelog/unreleased/kong or skip-changelog label added on PR if changelog is unnecessary. README.md
• There is a user-facing docs PR against https://github.com/Kong/docs.konghq.com - PUT DOCS PR HERE

Issue reference

Fix #[issue number]

[team-gateway-bot]

Successfully created cherry-pick PR for master:

• https://github.com/kong/kong-ee/pull/9179

[team-gateway-bot]

Cherry-pick failed for master, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally.

git remote add upstream https://github.com/kong/kong-ee
git fetch upstream master
git worktree add -d .worktree/cherry-pick-13021-to-master-to-upstream upstream/master
cd .worktree/cherry-pick-13021-to-master-to-upstream
git checkout -b cherry-pick-13021-to-master-to-upstream
ancref=$(git merge-base d112f3c09bf049fe4614dc5f38e45cba5adce0f7 9167936567c7ce285331a0aaf6e1ec9e23113b65)
git cherry-pick -x $ancref..9167936567c7ce285331a0aaf6e1ec9e23113b65

[team-gateway-bot]

Successfully created backport PR for release/3.7.x:

• [backport -> release/3.7.x] feat(db/schema): do not allow setting priority with traditional route in mixed mode #13100