Enhancement: Add randomized likes to Jetpack Like

### Impacted plugin

Jetpack

### What

I would like the option to display a randomized selection of people who have liked a post instead of the latest 5

### How

This is probably an edge-case but here's the issue: Jetpack Like will show the Gravatar images of the 5 users who have liked a post last. A sufficiently motivated actor can create 5 Gravatar accounts with a letter as their profile image and use that to display profanities inside the block.

This can also be used to display any 5-letter profanities, or a 4-letter word with an exclamation mark at the end ... and any variation.

We think the simplest solution would be to showcase a randomized order of users to prevent such an "attack" but any other solution is welcome too.

Start by locating the Jetpack Like implementation and the logic that selects the five users whose Gravatar images are displayed. Review how the current latest-five behavior works, then define and test a selection approach that avoids predictable profane displays while preserving the Like presentation.

Written by the indexing model from the issue text.