tests(router): remove duplicated reload_router()

[chronolaw]

Summary

KAG-5423

Separate setenv/unsetenv from misc to sys, then they will not depend on intenal.constants.

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]

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-13693-to-master-to-upstream upstream/master
cd .worktree/cherry-pick-13693-to-master-to-upstream
git checkout -b cherry-pick-13693-to-master-to-upstream
ancref=$(git merge-base a6ccbb1af2169a9edbf4491a91ecaf5d2d7fb067 c8cf5b703ebe4fe8ae785a8ae3dbf8af95034025)
git cherry-pick -x $ancref..c8cf5b703ebe4fe8ae785a8ae3dbf8af95034025