Clean up icms_version.php and move side effects into install/update handler(s)

[fiammybe]

Make icms_version.php primarily declarative by moving side effects into install/update handlers.

Checklist:

• Move all side effects (e.g. uploads dir creation) out of icms_version.php
• Move these to install/update scripts/handlers where applicable
• Make icms_version.php purely metadata/config only
• Update block/template metadata as needed