How to pass extra arguments to `frameset-restore` through `burly-open-url` ?

Hello,

How would you augment the `burly-open-url` entrypoint somehow with the key values from `frameset-restore` at least ? I’m open to make the PR for it if we can agree on the plan.

My use case :
I’d like to `reuse-frames` when I open a burly frames URL, so that when I open the URL I don’t have a new frame appearing, but instead my current frame is replaced with the URL. Imagine that I open the URL directly from `emacs-dashboard` when I start Emacs, so I really just want to reuse the frame I just opened.

https://github.com/emacs-mirror/emacs/blob/3af9e84ff59811734dcbb5d55e04e1fdb7051e77/lisp/frameset.el#L1139-L1143

I don’t know yet if I’d want to pass extra keys or not, as I didn’t play a lot with the function for now. But it’d be nice to control a little more how the frame is opened. I thought about :
- adding a lot of prefix args, but I already think it’s going to be a messy API
- adding a lot of `burly-` custom variables that would be used throughout, with some default values. I think it’s the easiest way, and matches the "style" of `burly-frameset-filter-alist` et al. But the issue becomes about "how do I override the defaults for 1 call ?"; and I think the only way to deal with it would be to `let-bind` the variables in a wrapping function, which is fine for me.
- storing extra information in the URL about how to open the URL later, but I thought it was a little too much work for the feature.

I hope I’m clear enough, and have a nice day,
Gerry