Social links variation transforms

[JosVelasco]

What problem does this address?

It is possible to duplicate a social link block from the icon toolbar or use keyboard shortcuts. Still, it cannot be transformed into another social icon variation. This would be handy for quickly inserting icons or updating them when necessary.

What is your proposed solution?

Clicking the block icon would open the sibling inserter pop-up, as suggested in this comment to transform it to another block variation.

There is already work here, but the blocks list is extensive. The sibling inserter would work better.

[krokodok]

Changing all the old twitter icons to new ones for a client's website right now and really wish this was possible. Since #50139 is merged now, does that mean we could implement this easily? I will try to work up the code to do so in the next days.

[krokodok]

I opened a PR for that: #56900