Add canonical Map arrays and builder

[AdamGS]

Rationale for this change

Building on the logical type and scalar support in #9107, this makes map-typed arrays constructible, canonicalizable, and serializable. A dedicated canonical representation preserves Map semantics instead of treating maps as ordinary lists of structs.

What changes are included in this PR?

• Adds the vortex.map canonical encoding, backed by ListView<Struct<key, value>> storage while retaining the Map dtype and keys_sorted assertion.
• Adds MapArray, validated construction, entry access, validity delegation, scalar access, serialization, and session registration.
• Adds MapBuilder and integrates Map values with generic builder and canonicalization paths, including empty, constant, and chunked arrays.
• Tests cover valid and malformed storage, nullable and empty values, duplicate and unsorted keys, builder append behavior, canonicalization, scalar access, and serialization round-trips.

What APIs are changed? Are there any user-facing changes?

This adds the public Map, MapArray, MapArrayExt, MapDataParts, and MapBuilder APIs. Canonical and CanonicalView gain Map variants and corresponding accessors, so exhaustive matches over those enums must handle Map arrays.

Map arrays can now be built, canonicalized, inspected, and serialized. Compute paths such as take, filter, masking, compression, and Arrow array transport continue to reject Map arrays at this point in the stack.

[codspeed-hq]

Merging this PR will improve performance by 20.19%

⚡ 1 improved benchmark
✅ 1841 untouched benchmarks
⏩ 55 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	take_map[(0.1, 1.0)]	2 ms	1.6 ms	+20.19%

Tip

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_{Comparing adamg/maptype-2 (b158bfe) with adamg/maptype-1 (a54e5f6)}

Footnotes

1. 55 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩