update the OffsetArray test helper

[jishnub]

Sync the OffsetArray test helper with the repo.

[johnnychen94]

The docstring and compat patch are not needed for test helper, but it doesn't matter much to include them.

This PR is required for #45371. As long as the CI is green, I believe it's okay to merge and update the test-only dependency.

[johnnychen94]

Since OffsetArrays more eagerly checks the overflow behavior, len=0 is indeed an undefined behavior so I agree to remove it. -- Specially handling length 0 array could also be problematic because user codes might do push!(parent(offset_vector), x).

This OffsetArray(Int[], typemax(Int)) issue is already caught in OffsetArrays codebase https://github.com/JuliaArrays/OffsetArrays.jl/blob/44f9b50c5428416c8baa76af882c820605c17082/test/runtests.jl#L518

[jishnub]

The length-0 case is also related to #45389

[jishnub]

I don't really understand the reported ambiguities. Eg:

(reshape(A::Main.OffsetArrays.OffsetArray, inds::Tuple{Vararg{Union{Colon, Int64}}}) in Main.OffsetArrays at /home/jishnu/julia/test/testhelpers/OffsetArrays.jl:564,
reshape(parent::AbstractVector, ::Tuple{Colon}) in Base at reshapedarray.jl:116)

but there's

reshape(A::OffsetVector{T} where T, ::Tuple{Colon}) in Main.OffsetArrays at /home/jishnu/julia/test/testhelpers/OffsetArrays.jl:561

which should remove this ambiguity? Also, the methods are an exact copy from OffsetArarys.jl, using which I don't obtain these ambiguities.

[jishnub]

Test failures seem unrelated at this point