Summary:
A menu to be shown when new colum button is added. It's give access to various diffrent shortcuts, like adding new column, unhiding existing ones, fast adding lookup columns or trigger one (authoriship or timestamp). Design document can be found here: https://grist.quip.com/CTgxAQv9Ghjt/Add-Columns-more-easily
To turn on this menu flag GRIST_NEW_COLUMN_MENU to 1
Test Plan: UI tests suite under nbrowser/GridViewNewColumnMenu.ts
Reviewers: jarek, georgegevoian
Reviewed By: georgegevoian
Subscribers: paulfitz
Differential Revision: https://phab.getgrist.com/D4074
