Factor topology into package: PlutoDependencyExplorer.jl

[fonsp]

We already did #2698 which means that people can find the references and definitions of an Expr in another package more easily. This PR factors out a second package that layers on top of ExpressionExplorer: given a list of Expr (i.e. a notebook of cells), in which order should the expressions be evaluated?

Not sure about the name PlutoReactiveCore

TODO:

• [x] Factor out the Cell. PlutoReactiveCore only uses it as a key (like Dict{Cell,ReactiveNode}), without accessing any of its fields. (This was the result of previous refactors.) To solve the dependency, it could be replaced with a UUID everywhere. But this will means lots of conversions everywhere in our code that's less charming. We could also use an AbstractCell type in PlutoReactiveCore, with a Cell <: AbstractCell in Pluto.
• [x] Factor our the PlutoRuner.@bind dependency used in the static macro expand of ExpressionExplorerExtras. Easiest is probably to write a copy of the macro inside PlutoReactiveCore, since it's only used for analysis.
• [x] Make sure that it works inside the Pluto codebase as a module, and put into a separate package afterwards.

[github-actions[bot]]

Try this Pull Request!

Open Julia and type:

  julia> import Pkg
  julia> Pkg.activate(temp=true)
  julia> Pkg.add(url="https://github.com/fonsp/Pluto.jl", rev="PlutoReactiveCore")
  julia> using Pluto

[fonsp]

@quildtide you would like this! Also check out ExpressionExplorer.jl

[fonsp]

@pankgeorg any name suggestions?

[fonsp]

@Pangoraw what do you think about this? It's ready now, but I'm starting to doubt a bit whether the rewriting work and increased complexity was worth it... But I guess it's nice to have this package?

[fonsp]

Yeah that's the thing, I don't have the capacity to use it right away, but I am planning to use it at some point. But I made the split right now so it's best to merge it now before we get conflicts?

[pankgeorg]

Not sure about the name PlutoReactiveCore

It feels that this isn't the reactive core; the reactive core uses the topology that this package outlines IIUC.

I'd call this ReactivityExplorer or DependencyExplorer or TopologyExplorer, following ExpressionExplorer or something

[fonsp]

Hmm but I like to keep Pluto in the name I think... because this package is more Pluto-specific and opinionated than ExpressionExplorer. Maybe PlutoDependencyExplorer?

[fonsp]

yolooo