tests/docker: update TiDB stack/TiFlash image registries and sanitize branch-tag variables#10721

Copilot wants to merge 3 commits into

feature/release-8.5-materialized-viewpingcap/tiflash:feature/release-8.5-materialized-viewfrom

copilot/update-image-repositoriespingcap/tiflash:copilot/update-image-repositoriesCopy head branch name to clipboard