Test failures with CategoricalArrays 1.0

I havne't been able to replicate it in CI, but I have replicated it on both a M1 Mac and and an x86-64 Ubuntu machine locally:

`BoundsError: attempt to access 3-element CategoricalArrays.CategoricalRefPool{Union{Missing, CategoricalValue{String, UInt32}}, CategoricalPool{String, UInt32}} with indices 0:2 at index [3]`

cc @nalimilan

```julia
# some dict encoding coverage: Error During Test at /home/ubuntu/arrow-julia/test/runtests.jl:339
Got exception outside of a @test
BoundsError: attempt to access 3-element CategoricalArrays.CategoricalRefPool{Union{Missing, CategoricalValue{String, UInt32}}, CategoricalPool{String, UInt32}} with indices 0:2 at index [3]
Stacktrace:
[1] throw_boundserror(A::CategoricalArrays.CategoricalRefPool{Union{Missing, CategoricalValue{String, UInt32}}, CategoricalPool{String, UInt32}}, I::Tuple{Int64})
@ Base ./abstractarray.jl:737
[2] checkbounds
@ ./abstractarray.jl:702 [inlined]
[3] getindex
@ ~/.julia/packages/CategoricalArrays/ptzwC/src/array.jl:1161 [inlined]
[4] getindex
@ ~/.julia/packages/ArrowTypes/IVpuP/src/ArrowTypes.jl:445 [inlined]
[5] iterate
@ ./abstractarray.jl:1216 [inlined]
[6] Arrow.ValidityBitmap(x::ToArrow{Union{Missing, String}, CategoricalArrays.CategoricalRefPool{Union{Missing, CategoricalValue{String, UInt32}}, CategoricalPool{String, UInt32}}})
@ Arrow ~/arrow-julia/src/arraytypes/arraytypes.jl:228
[7] arrowvector(::ListKind{true}, x::ToArrow{Union{Missing, String}, CategoricalArrays.CategoricalRefPool{Union{Missing, CategoricalValue{String, UInt32}}, CategoricalPool{String, UInt32}}}, i::Int64, nl::Int64, fi::Int64, de::Dict{Int64, Any}, ded::Vector{Arrow.DictEncoding}, meta::Base.ImmutableDict{String, String}; largelists::Bool, kw::@Kwargs{dictencode::Bool, maxdepth::Int64, dictencodenested::Bool, compression::Nothing})
@ Arrow ~/arrow-julia/src/arraytypes/list.jl:226
[8] arrowvector
@ ~/arrow-julia/src/arraytypes/list.jl:224 [inlined]
[9] #arrowvector#10
@ ~/arrow-julia/src/arraytypes/arraytypes.jl:150 [inlined]
[10] arrowvector
@ ~/arrow-julia/src/arraytypes/arraytypes.jl:148 [inlined]
[11] arrowvector(x::CategoricalArrays.CategoricalRefPool{Union{Missing, CategoricalValue{String, UInt32}}, CategoricalPool{String, UInt32}}, i::Int64, nl::Int64, fi::Int64, de::Dict{Int64, Any}, ded::Vector{Arrow.DictEncoding}, meta::Nothing; dictencoding::Bool, dictencode::Bool, maxdepth::Int64, kw::@Kwargs{dictencodenested::Bool, compression::Nothing})
@ Arrow ~/arrow-julia/src/arraytypes/arraytypes.jl:113
[12] arrowvector(::DictEncodedKind, x::Arrow.DictEncode{Union{Missing, CategoricalValue{String, UInt32}}, CategoricalVector{Union{Missing, String}, UInt32, String, CategoricalValue{String, UInt32}, Missing}}, i::Int64, nl::Int64, fi::Int64, de::Dict{Int64, Any}, ded::Vector{Arrow.DictEncoding}, meta::Base.ImmutableDict{String, String}; dictencode::Bool, dictencodenested::Bool, kw::@Kwargs{maxdepth::Int64, compression::Nothing})
@ Arrow ~/arrow-julia/src/arraytypes/dictencoding.jl:236
[13] arrowvector
@ ~/arrow-julia/src/arraytypes/dictencoding.jl:202 [inlined]
[14] #arrowvector#10
@ ~/arrow-julia/src/arraytypes/arraytypes.jl:150 [inlined]
[15] arrowvector
@ ~/arrow-julia/src/arraytypes/arraytypes.jl:148 [inlined]
[16] arrowvector(x::CategoricalVector{Union{Missing, String}, UInt32, String, CategoricalValue{String, UInt32}, Missing}, i::Int64, nl::Int64, fi::Int64, de::Dict{Int64, Any}, ded::Vector{Arrow.DictEncoding}, meta::Nothing; dictencoding::Bool, dictencode::Bool, maxdepth::Int64, kw::@Kwargs{compression::Nothing})
@ Arrow ~/arrow-julia/src/arraytypes/arraytypes.jl:113
[17] arrowvector
@ ~/arrow-julia/src/arraytypes/arraytypes.jl:68 [inlined]
[18] toarrowvector(x::CategoricalVector{Union{Missing, String}, UInt32, String, CategoricalValue{String, UInt32}, Missing}, i::Int64, de::Dict{Int64, Any}, ded::Vector{Arrow.DictEncoding}, meta::Nothing; compression::Nothing, kw::@Kwargs{})
@ Arrow ~/arrow-julia/src/arraytypes/arraytypes.jl:47
[19] toarrowvector
@ ~/arrow-julia/src/arraytypes/arraytypes.jl:36 [inlined]
[20] toarrowvector(x::CategoricalVector{Union{Missing, String}, UInt32, String, CategoricalValue{String, UInt32}, Missing})
@ Arrow ~/arrow-julia/src/arraytypes/arraytypes.jl:36
[21] macro expansion
@ ~/arrow-julia/test/runtests.jl:347 [inlined]
[22] macro expansion
@ ~/.julia/juliaup/julia-1.10.10+0.x64.linux.gnu/share/julia/stdlib/v1.10/Test/src/Test.jl:1577 [inlined]
[23] macro expansion
@ ~/arrow-julia/test/runtests.jl:341 [inlined]
[24] macro expansion
@ ~/.julia/juliaup/julia-1.10.10+0.x64.linux.gnu/share/julia/stdlib/v1.10/Test/src/Test.jl:1577 [inlined]
[25] macro expansion
@ ~/arrow-julia/test/runtests.jl:115 [inlined]
[26] macro expansion
@ ~/.julia/juliaup/julia-1.10.10+0.x64.linux.gnu/share/julia/stdlib/v1.10/Test/src/Test.jl:1577 [inlined]
[27] top-level scope
@ ~/arrow-julia/test/runtests.jl:54
[28] include(fname::String)
@ Base.MainInclude ./client.jl:494
[29] top-level scope
@ none:6
[30] eval
@ ./boot.jl:385 [inlined]
[31] exec_options(opts::Base.JLOptions)
@ Base ./client.jl:296
[32] _start()
@ Base ./client.jl:557
```

Start with the dict encoding coverage around test/runtests.jl:339-347 and inspect the CategoricalArrays access reported at src/arraytypes/arraytypes.jl:228, along with the ArrowTypes frame in the stack trace. Reproduce locally with CategoricalArrays 1.0 and confirm the relevant tests complete without the BoundsError.

Written by the indexing model from the issue text.