feat(version) set version to v1.6.8

chore(version): prepare v1.6.6 version

chore(version): change version to v1.6.5

fix(version): fix version

(cherry picked from commit 7cb6b7c7d43acc638c551a1b87e31ebaa70f27fc)

ci: support create cluster and run conformance tests on volcengine

- Add scripts to install kubernetes cluster on volcengine.
- Add scripts to run conformance tests.