Update bench version from 5.15.2 to latest

[ankush]

diff: frappe/bench@v5.15.2...v5.16.1

Main changes:

• Fixes failures where __version__ is missing in apps - fix: version check backward compatibility bench#1409
• chdir monkey patch is done earlier for clearing command cache - fix(cli): Setup chdir patch earlier bench#1421

[ankush]

TODO:

• add new one as option in allowed bench versions
• update all internal RGs
• nightly bench
• update saas RG
• update public bench RGs
• make it default in code and update all private bench RGs which are untouched.

[ankush]

This update is now even more required because of:

• cache in get-app
• validate deps
• yarn install cache fix

[18alantom]

Enabled Release Groups on Version 15 and Nightly have been bumped to 5.22.0. They should be using 5.22.0 from the next deploy.

Default bench versions have been set to 5.22.0 in #1430.