fix: support missing columns in Mosaic reads

[QuakeWang]

Purpose

Linked issue: #378

Mosaic reads used to validate the full requested schema before checking the physical Mosaic file schema. When a requested column was missing from an older Mosaic file, an unsupported type in that missing column could fail the read before DataFileReader had a chance to fill it with nulls.

Brief change log

• Filter Mosaic projections by the physical file schema before validating supported Mosaic types.
• Return empty batches with the correct row count when all requested Mosaic columns are physically missing.
• Keep missing column null filling in DataFileReader.
• Add Mosaic reader tests for missing columns, missing unsupported columns, all-missing projections, and row selection.
• Add a DataFileReader test covering null fill for a physically missing Mosaic column.

Tests

• cargo fmt --all -- --check
• cargo test -p paimon --features mosaic arrow::format::mosaic -- --nocapture
• cargo test -p paimon --features mosaic table::data_file_reader -- --nocapture
• cargo check -p paimon-datafusion --features mosaic
• cargo clippy -p paimon --features mosaic --tests -- -D warnings

API and Format

Documentation

[JingsongLi]

+1