Spreadsheet side panels now use the central store mechanism instead of the previous environment-based approach. This internal cleanup helps keep spreadsheet features such as charts, filters, lists, pivots, and comments more consistent and easier to maintain without changing the user workflow.

This commit adapts the spreadsheet to use the side panel method from the store instead of the env.

Task: 6566084

The spreadsheet interface now relies on the application's central store to manage side panels instead of passing that behavior through the environment. This internal cleanup should make spreadsheet-related screens easier to maintain while keeping the user experience unchanged.

Description of the issue/feature this PR addresses:

Current behavior before PR:

Desired behavior after PR is merged:




---
I confirm I have signed the CLA and read the PR guidelines at www.odoo.com/submit-pr