QA: ExplicitImports no_implicit_imports — make implicit imports explicit

Tracking issue for the ExplicitImports check_no_implicit_imports finding, marked @test_broken via ei_broken = (:no_implicit_imports,) in the new run_qa-based QA group (PR converting QA onto the SciMLTesting run_qa v1.6 form + ExplicitImports).

DiffEqGPU relies on bare using of many heavy dependencies (KernelAbstractions, SciMLBase, DiffEqBase, StaticArrays, LinearAlgebra, ForwardDiff, Distributed, RecursiveArrayTools, SimpleDiffEq, ...), so ExplicitImports.check_no_implicit_imports(DiffEqGPU) reports ~75 implicitly-imported names. Converting each to an explicit using X: a, b, c is a large, mechanical-but-risky refactor (much of the surface is GPU-kernel macro usage such as @kernel, @Const, @index, @muladd, @unpack, @set), so it is deferred rather than done as part of the QA conversion.

The check is currently recorded as Broken (not Fail) so the QA lane stays green; once the implicit imports are made explicit, the @test_broken flips to an Unexpected Pass and :no_implicit_imports should be dropped from ei_broken.

Full implicit-import list (Julia LTS, ExplicitImports 1.15.0):

Adapt, adapt (Adapt)
BrownFullBasicInit (DiffEqBase)
Distributed, nprocs, pmap (Distributed)
DocStringExtensions (DocStringExtensions)
ForwardDiff (ForwardDiff)
KernelAbstractions, @Const, @index, @kernel, CPU (KernelAbstractions)
LinearAlgebra, I, LowerTriangular, NoPivot, RowMaximum, SingularException, UpperTriangular, det (LinearAlgebra)
LinearSolve (LinearSolve)
MuladdMacro, @muladd (MuladdMacro)
Parameters; @unpack (UnPack)
Random (Random)
RecursiveArrayTools, VectorOfArray (RecursiveArrayTools)
Setfield, @set, @set! (Setfield)
SimpleDiffEq, GPUSimpleATsit5, GPUSimpleAVern7, GPUSimpleAVern9, GPUSimpleTsit5, GPUSimpleVern7, GPUSimpleVern9, SimpleEM (SimpleDiffEq)
DiffEqBase (DiffEqBase)
ODEProblem, SDEProblem, SciMLBase, CallbackSet, CheckInit, ContinuousCallback, DiscreteCallback, EnsembleDistributed, EnsembleProblem, EnsembleSerial, EnsembleSolution, EnsembleThreads, ODEFunction, ReturnCode, SDEFunction, VectorContinuousCallback, remake, terminate! (SciMLBase)
solve (CommonSolve)
SimpleNonlinearSolve (SimpleNonlinearSolve)
StaticArrays (StaticArrays); MArray, MMatrix, SArray, SMatrix, SVector, Size, StaticMatrix, StaticVector, similar_type (StaticArraysCore)
setindex (Base)

Start with the new run_qa-based QA group and its ExplicitImports check_no_implicit_imports entry, using the listed implicit-import report as the scope. Make the imports explicit across the affected DiffEqGPU code, then verify that the @test_broken check becomes an Unexpected Pass and that :no_implicit_imports can be removed from ei_broken.