feat: Implement issorted for AbstractGPUArray without scalar indexing.

[shreyas-omkar]

Fix for #635

Base.issorted on AbstractGPUArray currently falls back to scalar iteration, which triggers scalar indexing errors and prevents correct usage on GPU-backed arrays.

This PR introduces a GPU-native implementation of issorted using a kernel-based approach, ensuring the operation executes entirely on the device.

Tests

(GPUArrays with base as test_args)

---

(GPUArrays)

[shreyas-omkar]

@kshyatt please review.

[kshyatt]

Thanks for getting to this so quickly! I'm at a conference today so may not get to it immediately but perhaps @maleadt has spare time? If not I'll look on Monday.

[shreyas-omkar]

@maleadt I have removed the unnecessary using KernelAbstractions import as suggested

I initially tried using Base.Order.lt(ord, a, b), but this results in invalid GPU IR.
To avoid this, the current implementation resolves order and rev on the host and passes plain lt / by functions into the kernel, which keeps the device code simple and GPU-safe.

Please let me know if I'm missing something.

[maleadt]

Seems to generate code fine? What issue exact were you running into?

julia> code_llvm(Base.lt, Tuple{Base.Order.ForwardOrdering, Int, Int})
; Function Signature: lt(Base.Order.ForwardOrdering, Int64, Int64)
;  @ ordering.jl:118 within `lt`
define i8 @julia_lt_3166(i64 signext %"a::Int64", i64 signext %"b::Int64") #0 {
top:
; ┌ @ operators.jl:431 within `isless`
; │┌ @ int.jl:83 within `<`
    %0 = icmp slt i64 %"a::Int64", %"b::Int64"
    %1 = zext i1 %0 to i8
    ret i8 %1
; └└
}

julia> code_llvm(Base.lt, Tuple{Base.Order.ReverseOrdering{Base.Order.ForwardOrdering}, Int, Int})
; Function Signature: lt(Base.Order.ReverseOrdering{Base.Order.ForwardOrdering}, Int64, Int64)
;  @ ordering.jl:119 within `lt`
define i8 @julia_lt_3169(i64 signext %"a::Int64", i64 signext %"b::Int64") #0 {
top:
;  @ ordering.jl:119 within `lt` @ ordering.jl:118
; ┌ @ operators.jl:431 within `isless`
; │┌ @ int.jl:83 within `<`
    %0 = icmp slt i64 %"b::Int64", %"a::Int64"
    %1 = zext i1 %0 to i8
    ret i8 %1
; └└
}

[github-actions]

Your PR no longer requires formatting changes. Thank you for your contribution!

[shreyas-omkar]

Hi @maleadt . I have made the changes that you've suggested.

[maleadt]

Thanks for the PR!