Add DEIIPFunctionWrapper structs to reduce stack trace length

[ChrisRackauckas-Claude]

Summary

Addresses part of SciML/DifferentialEquations.jl#1128 (FunctionWrappersWrapper bloat in stack traces).

Introduces wrapper structs (not type aliases) around FunctionWrappersWrapper to dramatically shorten type strings in stack traces:

• 1-wrapper (non-ForwardDiff): ~170 chars → ~90 chars (47% reduction)
• 4-wrapper (ForwardDiff): ~1,077 chars → ~350 chars (67% reduction)

Key insight: const Foo{T} = Bar{T} type aliases do NOT change how typeof(x) prints in Julia — only new struct types reduce the printed representation.

New structs (defined in DiffEqBase, exported)

• DEIIPFunctionWrapper{duType, uType, pType, tType} — wraps a FunctionWrappersWrapper with 1 FunctionWrapper for solvers that don't use ForwardDiff (e.g. Tsit5, Verner)
• DEIIPFunctionWrapperForwardDiff{T1, T2, T3, T4, dT1, dT2, dT4} — wraps a FunctionWrappersWrapper with 4 FunctionWrapper entries covering base/dual-state/dual-time/dual-both argument combinations
• AnyFunctionWrapper — Union{FunctionWrappersWrapper, DEIIPFunctionWrapper, DEIIPFunctionWrapperForwardDiff} for isa checks
• DEIIPFunctionWrapperVF64{pType} — VF64-specialized alias for DEIIPFunctionWrapper
• wrapfun_iip_simple(ff, du, u, p, t) — constructor that always creates a 1-wrapper, avoiding ForwardDiff extension backedges

In ForwardDiff extension (access via Base.get_extension)

• DEIIPFunctionWrapperForwardDiffVF64{pType} — VF64-specialized alias
• ODEDualTag — ForwardDiff.Tag{OrdinaryDiffEqTag, Float64}
• ODEDualType — ForwardDiff.Dual{ODEDualTag, Float64, 1}

Changes to existing code

• solve.jl: Uses AnyFunctionWrapper instead of FunctionWrappersWrappers.FunctionWrappersWrapper for isa checks; uses wrapfun_iip_simple for the non-ForwardDiff path
• ForwardDiff extension's wrapfun_iip(ff, inputs::Tuple{T1,T2,T3,T4}) now returns DEIIPFunctionWrapperForwardDiff(inner) instead of raw FunctionWrappersWrapper
• Both structs delegate calls via (f::DEIIPFunctionWrapper)(args...) = f.fw(args...)
• Both support isfunctionwrapper and unwrapped_f

Usage example (downstream package)

using DiffEqBase: DEIIPFunctionWrapperVF64

# ForwardDiff-specific aliases from the extension
const FDExt = Base.get_extension(DiffEqBase, :DiffEqBaseForwardDiffExt)
const DEIIPFWForwardDiffVF64 = FDExt.DEIIPFunctionWrapperForwardDiffVF64

# Use in struct field annotations
mutable struct ODEIntegratorVF64{pType, ...}
    f_simple::DEIIPFunctionWrapperVF64{pType}
    # or for stiff solvers:
    f_dual::DEIIPFWForwardDiffVF64{pType}
end

Test plan

• New function_wrapper_aliases.jl test file (27 tests) verifying:
  • DEIIPFunctionWrapper struct creation and type matching
  • DEIIPFunctionWrapperVF64 alias with both Vector{Float64} and NullParameters
  • ODEDualTag and ODEDualType equal the expected ForwardDiff types
  • DEIIPFunctionWrapperForwardDiff struct from wrapfun_iip
  • DEIIPFunctionWrapperForwardDiffVF64 alias
  • AnyFunctionWrapper union matching
  • Call operator, isfunctionwrapper
  • Type string does NOT contain "FunctionWrappersWrapper" (key stack trace test)
  • wrapfun_iip_simple always produces 1-wrapper even with ForwardDiff loaded
  • 7-wrapper default does NOT match 4-wrapper struct
• Full Pkg.test() passes (all existing tests unaffected)

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