Add borg assimilatte as borg create alias #10540

While reading the migration guide for borg 2, I noted the following:

Archive names don’t need to be unique anymore. To the contrary: It is now strongly recommended to use the identical name for borg create within the same series of archives to make borg work more efficiently. The name now identifies a series of archives; to identify a single archive, please use aid:, e.g., borg delete aid:d34db33f

Forgetting the internal reasons, from the user perspective, this model makes much more sense to me, and it was a bit confusing at first in borg 1.x to wrap my head around the fact that I needed a new name every time I wanted to back up the same computer.
However, in this model, the name borg create doesn't make as much sense: true, we are still creating an archive, but it feels less intuitive to "create" something with the same name repeatedly as the most common operation of the software.
Pondering this, I came across the natural alternative: lean in to the Borg theme.

I propose adding an alias for borg create named borg assimilate. I argue that this makes for a more intuitive mental model in the more common case that the archive stream already exists, and is still easy to accept in the case that it doesn't ("create if not already present" is a common enough model for any archive tool).
In addition, it makes for a good joke.