feat: add Mosaic row-group predicate pruning

[QuakeWang]

Purpose

Linked issue: Related to #378

Mosaic reads previously treated data predicates as residual only, so row groups were read even when Mosaic row-group statistics could prove they could not match.

This PR adds conservative row-group predicate pruning for Mosaic files while preserving residual filtering semantics.

Brief change log

• Add a Mosaic StatsAccessor over row-group ColumnStats.
• Map file-level Paimon fields to Mosaic column indices by name.
• Convert supported Mosaic stats values into Paimon Datum for shared stats pruning.
• Fail open when stats are missing or cannot be interpreted safely.
• Update ReadBuilder docs to describe generic format-level reader pruning.

Tests

• cargo test -p paimon --features mosaic arrow::format::mosaic::tests -- --nocapture
• cargo fmt --check

API and Format

Documentation