(fix) site_cache_dir() must return DVC_SITE_CACHE_DIR if it exists#10776

skshetry merged 3 commits intotreeverse:maintreeverse/dvc:mainfrom

rgoya:fix_do_not_ignore_site_cache_dir_env_varrgoya/dvc:fix_do_not_ignore_site_cache_dir_env_varCopy head branch name to clipboard