rework permission methods

## Overview

permissions methods are located in the client and in a the spreadsheet, this is not right, only 1 object should provide a single way to add/list/delete permission.

## Details

The gspread client and the spreadsheet object allow a user to insert permissions, but only the client allows a user to list/remove a permission.

The spreadsheet object does not take the same kind of arguments as the gspread client does, this is confusing.

We should have a unified way of inserting/listing/deleting permissions.

This Issue is here to:

- discuss it
- where should they be located
- what kind of argument should they take each
- plan it
- do we add the new methods and keep the old one too (marked as deprecated)
- do we find an internal hidden way to make both work
- when do we release them, next major release or sooner

Start by comparing the permission methods on the gspread client and spreadsheet objects, including their current arguments and add/list/delete coverage. Define where the unified methods belong, how arguments and backward compatibility should work, and what release timing is intended before changing the API.

Written by the indexing model from the issue text.