perf(arrow/array): reuse full chunks in NewChunkedSlice

[fallintoplace]

What

• Reuse the original chunk when NewChunkedSlice selects the full chunk.
• Keep using NewSlice for partial chunks.
• Preserve the existing ownership pattern by retaining the reused chunks before passing them to NewChunked.

This avoids creating an ArrayData and typed array wrapper for every full chunk in an aligned slice.

Benchmark

Apple M1 Pro, Go 1.26.3, 7 samples, one CPU:

go test -vet=off ./arrow/array -run '^$' -bench '^BenchmarkNewChunkedSlice$' -benchmem -benchtime=150ms -count=7 -cpu=1

Aligned, non-null input with 64 rows per chunk:

Chunks	Before	After
64	10.122 us, 13.312 KiB, 131 allocs	2.264 us, 2.312 KiB, 3 allocs
1,024	173.15 us, 212.06 KiB, 2,051 allocs	37.14 us, 36.06 KiB, 3 allocs
8,192	1.383 ms, 1.664 MiB, 16,387 allocs	272.3 us, 256.1 KiB, 3 allocs

Across all 12 benchmark cases, the geometric mean changed from 136.8 us to 29.24 us (-78.63%), 167.5 KiB to 28.44 KiB (-83.02%), and 1,639 to 4.583 allocations (-99.72%).

Tests

• PARQUET_TEST_DATA=parquet-testing/data ARROW_TEST_DATA=arrow-testing/data go test ./... -count=1