fetch all the variants of a graph

[ThomasJamesCrawford]

Description

We create a new variant of our graph for each unique ephemeral environment we spin up.

We want to be able to cleanup these variants when they're no longer required.

We can delete the variant if we know the exact name, but if we lose track of the possible variants there's no way to list them all out to find ones we no longer need.

Just something like this would be really helpful rover supergraph list <graphname>

output

variant-1
variant-2
variant-3

[gnsallman]

+1 on this

[jaska120]

It would be great to see this added as well as rover graph list <graphname>. We also create a new variant for each unique ephemeral environment we spin up.