Upgrade codemirror with new parser

[fonsp]

@savq did incredible work on the Julia parser! https://github.com/JuliaPluto/lezer-julia/pull/7

Fix https://github.com/fonsp/Pluto.jl/issues/2943

[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="codemirror-savq")
julia> using Pluto

[fonsp]

@savq mabye you could help with updates to lezer_template and scopestate_statefield? I think the rest is easy enough for me :)

[fonsp]

This PR got stuck because of the pattern matching code by dralletje. I gave it a try but this is way to hard to update, I'm declaring it unmaintainable!

Since we barely use the pattern matching and scopestate system, I will look into removing it and rewriting functionality into simpler (less precise) tree traversal code.

[fonsp]

Ready! Merging soon :)