Create ad-hoc plots

I would like to be able to create *graphical* plots, other than those already defined in `dvc.yaml`, inside Studio. The reasoning for this is that I have plots (=csv tables) with many columns, but to avoid general clutter, I only produce 1 or 2 graphical plots from them, showing the metrics that matter the most.

However, when examining the results, I sometimes want to be able to see graphical plots with other column combinations as well - this can be done locally using `dvc plots show`, but such an option is missing in Studio. These plots are "temporary" - I don't want them to be displayed permanently (otherwise I would define then in `dvc.yaml`).

For my use case, being able to create simple linear plots would suffice