Offer paging for boost carousel and disable animations

**Is your feature request related to a problem? Please describe.**

While its nice to have a boost count displayed, it's annoying to have to scroll through: arrow buttons and shortcut keys move posts by +/- 1 only, and the animation of every single scroll is absolutely annoying (for me). I need a faster and less annoying way to navigate the carousel.

**Describe the solution you'd like**
Offer paging as an alternative, i.e. moving right or left by the number of boost columns that are shown, instead of +/- 1. Ideally, page numbers would appear between the arrow buttons, so I cn quickly move to a page that I have remembered.
Make "movement" animations optional.

**Describe alternatives you've considered**
A tiny scroll bar like for the account avatars in the Catch-up window is an even worse alternative: tedious to move to and hit, and constantly vanishing.

**Additional context**
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No files or tests are named. Locate the boost carousel entry point and inspect the existing arrow and keyboard movement, then determine how many boost columns are visible; done means paging moves by that count, page numbers can be selected, and movement animations can be disabled without breaking navigation.

Written by the indexing model from the issue text.