Qualify constructor methods in extensions

[danielwe]

Checklist

• (NA) Appropriate tests were added
• Any code changes were done in a way that does not break public API
• (NA) All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• (NA) Any new documentation only uses public API

Additional context

Adds module qualification to constructor methods added in extensions. The lack of this was causing precompilation warnings since Julia 1.12, e.g.:

┌ Surrogates → SurrogatesAbstractGPsExt
│  WARNING: Constructor for type "AbstractGPSurrogate" was extended in `SurrogatesAbstractGPsExt` without explicit qualification or import.
│    NOTE: Assumed "AbstractGPSurrogate" refers to `Surrogates.AbstractGPSurrogate`. This behavior is deprecated and may differ in future versions.`
│    NOTE: This behavior may have differed in Julia versions prior to 1.12.
│    Hint: If you intended to create a new generic function of the same name, use `function AbstractGPSurrogate end`.
│    Hint: To silence the warning, qualify `AbstractGPSurrogate` as `Surrogates.AbstractGPSurrogate` in the method signature or explicitly `import Surrogates: AbstractGPSurrogate`.
└

To reliably reproduce the warnings (and the lack of them after this fix), the extensions should not be in your compilation cache. The easiest is to use a temporary depot:

JULIA_DEPOT_PATH="/tmp/tmpdepot:" julia -e 'using Pkg; Pkg.add(["Surrogates", "AbstractGPs", "Flux", "LIBSVM", "PolyChaos", "XGBoost"])'
# [...]
# Precompiling packages finished.
#   211 dependencies successfully precompiled in 56 seconds. 39 already precompiled.
#   5 dependencies had output during precompilation:
# ┌ Surrogates → SurrogatesAbstractGPsExt
# │  WARNING: Constructor for type "AbstractGPSurrogate" was extended in `SurrogatesAbstractGPsExt` without explicit qualification or import.
# [...]

[danielwe]

No clue about the CI format check. runic-action: julia is a required dependency but does not seem to be available. Seems to have worked fine in #547 just a few days ago.