fix(variant): support FixedSizeList across shredded APIs

[cakeni]

Which issue does this PR close?

• Closes [Variant] Reconcile FixedSizeList support across shredded Variant APIs #10616.

Rationale for this change

shred_variant and unshred_variant already support FixedSizeList, but VariantArray::try_new rejected the resulting typed value and indexed variant_get traversal skipped it. Supporting it at both remaining boundaries makes the shredded Variant APIs consistent.

What changes are included in this PR?

• Accept and recursively canonicalize FixedSizeList typed values.
• Traverse fixed-size lists through the existing ListLikeArray path.
• Extend construction and list-like path tests to cover fixed-size lists.

Are these changes tested?

• cargo +stable-x86_64-pc-windows-gnu test -p parquet-variant-compute --lib (347 passed)
• cargo fmt --all -- --check
• git diff --check

Are there any user-facing changes?

Shredded fixed-size-list typed values can now be read with VariantArray::try_new and traversed by index with variant_get. No public API signatures change.