Odoo Studio now relies on the shared list selection behavior provided by the main platform instead of maintaining its own version. This keeps Studio more consistent with the rest of Odoo and reduces duplicated maintenance work, with no expected change for end users.

This commit is the counter part of a change done in odoo/odoo#212148 which adds the `selection` getter on StaticList. Studio doesn't need to define it anymore.

Spreadsheet export support is now loaded only when it is actually needed, rather than during general module startup. This should reduce unnecessary processing for users who are not exporting Excel files while keeping report export behavior unchanged.

odoo/odoo#212411