Fix forward zero-set warning for non-float types

[vchuravy]

The Enzyme compiler previously emitted a warning during forward mode AD when doing an arraycopy or genericmemory_copy_slice on an inactive value that had an active return (necessitating zero-initialization of the shadow memory). When the precise runtime type of the underlying array couldn't be definitively determined at compile time (or if it was not a basic Float array), the compiler was falling back to emitting a raw memset to zero out the memory.

This patch introduces post_arraycopy_makezero and post_genericmemcpy_makezero which dynamically use Enzyme.make_zero! to zero initialize the arrays safely if they are not plain floats.

Co-authored-by: Antigravity antigravity@google.com

fixes #1790

[github-actions]

Benchmark Results

	main	ce9a41d...	main / ce9a41d...
basics/make_zero/namedtuple	0.0561 ± 0.0075 μs	0.0567 ± 0.0067 μs	0.991 ± 0.18
basics/make_zero/struct	0.245 ± 0.0097 μs	0.256 ± 0.0072 μs	0.958 ± 0.047
basics/overhead	4.32 ± 0.001 ns	3.17 ± 0.018 ns	1.36 ± 0.0077
basics/remake_zero!/namedtuple	0.229 ± 0.014 μs	0.222 ± 0.0091 μs	1.03 ± 0.074
basics/remake_zero!/struct	0.223 ± 0.012 μs	0.225 ± 0.013 μs	0.993 ± 0.079
fold_broadcast/multidim_sum_bcast/1D	10.8 ± 1.3 μs	10.9 ± 1.2 μs	0.994 ± 0.17
fold_broadcast/multidim_sum_bcast/2D	12.1 ± 0.34 μs	12.1 ± 0.36 μs	0.999 ± 0.041
time_to_load	1.05 ± 0.011 s	1.06 ± 0.018 s	0.992 ± 0.02

Benchmark Plots

A plot of the benchmark results has been uploaded as an artifact at https://github.com/EnzymeAD/Enzyme.jl/actions/runs/25424541595/artifacts/6825870086.