Cut short extension load cycles during precompilation

[IanButterworth]

Depends on

• Fix PkgId repr #52795
• Add nested precomp highlight debug #53111

Builds on #53111
Fixes #53081

Cuts the cycle short and highlights when two or more extensions are each triggered during the precompilation of eachother, which causes a dependency cycle in nested precompilation that was seen in #53081.

Note if this is considered safe, the @warns could just be @debugs and the user doesn't need to be notified.

i.e. on master this confusing error occurs, and it's actually coming from a double nested precompile worker precompiling SymbolicsForwardDiffExt but trying to load SymbolicsPreallocationToolsExt which the parent worker is in the process of precompiling

(@v1.11) pkg> precompile
Precompiling project...
  103 dependencies successfully precompiled in 34 seconds. 40 already precompiled.
  1 dependency had output during precompilation:
┌ Symbolics → SymbolicsPreallocationToolsExt
│  ┌ Warning: Module SymbolicsPreallocationToolsExt with build ID ffffffff-ffff-ffff-0008-f643010bcdb7 is missing from the cache.
│  │ This may mean SymbolicsPreallocationToolsExt [d479e226-fb54-5ebe-a75e-a7af7f39127f] does not support precompilation but is imported by a module that does.
│  └ @ Base loading.jl:2121
│  ┌ Error: Error during loading of extension SymbolicsPreallocationToolsExt of Symbolics, use `Base.retry_load_extensions()` to retry.

With this PR

(@v1.11) pkg> precompile
Precompiling project...
  103 dependencies successfully precompiled in 36 seconds. 40 already precompiled.
  2 dependencies had output during precompilation:
┌ FillArrays → FillArraysPDMatsExt
│  ┌ Warning: Dependency cycle detected in extension precompilation: FillArraysPDMatsExt > FillArraysSparseArraysExt > FillArraysPDMatsExt
│  └ @ Base loading.jl:1396
└  
┌ Symbolics → SymbolicsPreallocationToolsExt
│  ┌ Warning: Dependency cycle detected in extension precompilation: SymbolicsPreallocationToolsExt > SymbolicsForwardDiffExt > SymbolicsPreallocationToolsExt
│  └ @ Base loading.jl:1396
└ 

The cycle issue being this strong dependency branch

Symbolics > SymbolicUtils > LabelledArrays > PreallocationTools > ForwardDiff

triggers both of these Symbolics extensions without the need for any further packages present.

[extensions]
SymbolicsForwardDiffExt = "ForwardDiff"
SymbolicsPreallocationToolsExt = ["ForwardDiff", "PreallocationTools"]

So they both get triggered during the precompilation job of the other one.

Note that FillArraysPDMatsExt doesn't error on master like SymbolicsPreallocationToolsExt does. Not sure why not.

cc. @ChrisRackauckas

[KristofferC]

This seems better than the status quo so we should try it out imo.

[oscardssmith]

Should this be backported to 1.10?

[IanButterworth]

@KristofferC I've made this a @debug, so will silently work now, as I don't think there's much to teach the user about what not to do?

[KristofferC]

I guess we should add a test.

Should be enough to generate A, B, C, D make, extension AExtC, AExtD, and make A depend on B and make B depend on C, D?

[IanButterworth]

Not needed as we now skip cycles in extensions by not precompiling those extensions until loading time (where it somehow works) re. #53972

cc. @KristofferC