Add possibility to add custom bulk operations

[haringsrob]

Discussed in #1831

^{Originally posted by vladimirmartsul September 24, 2022}
Hi! Please help me to solve two tasks

1. I need to add custom bulk action on the listing page. For example, "Export selected elements". It's important for me
2. I need to add similar "Export" button to each row's actions on the listing page. It nice to have, but not critical for me.

I'm using Twill 2.9 and can upgrade to 3. I know how to register custom route and write action's logic in the controller, but I'm stuck with interface buttons.