perf: avoid expanding Mosaic row selections

[QuakeWang]

Purpose

Mosaic row selection previously expanded each selected row range into a UInt64Array of per-row indices before applying take. For large contiguous ranges, this makes memory and CPU cost proportional to the selected row count even though the input is already range-based.

Brief change log

• Keep Mosaic row selections as row-group-local (offset, len) slices.
• Apply a single selected range with RecordBatch::slice.
• Apply multiple selected ranges with concat_batches.
• Preserve row counts for empty/all-missing projections.
• Add coverage to ensure large selections stay range-based.

Tests

• cargo clippy --all-targets --workspace --features fulltext,vortex,mosaic -- -D warnings
• cargo test -p paimon --all-targets --features fulltext,vortex,mosaic test_mosaic
• cargo test -p paimon --all-targets --features fulltext,vortex,mosaic arrow::format::mosaic::tests

API and Format

Documentation