[6.x] Update site:clear config stubs to match current defaults

[lazerg]

The site:clear command was using outdated config file stubs that were missing several configuration options introduced in recent versions. This caused the config files to differ after running site:clear compared to a fresh installation.

The stubs for stache.php and users.php have been updated to include all current configuration options, including cache_store, warming optimizations, and user authentication features like two-factor authentication and impersonation settings.

Fixes #14737

[lazerg]

The failing check is StarterKits\ExportTest on the prefer-lowest matrix, where the resolved testbench skeleton doesn't include the welcome.blade.php and errors views those tests expect. That's unrelated to this change (which only updates the site:clear config stubs), and looks intermittent since the same cells pass on other PRs off the same base.