[core][mosaic] Preserve projected raw reads

[jianguotian]

Purpose

RawFileSplitRead can be reused with different projected RowType values, but its cached FormatReaderMapping entries are keyed only by file schema and format. Reconfiguring the reader can therefore reuse a stale projection. In addition, lazily-created file readers need to retain the output type selected when each reader is created.

This PR:

• invalidates cached format mappings only when withReadType receives a different RowType;
• captures the current output type when a reader is created;
• passes that same type through the mapping builder, lazy file-reader suppliers, and DataFileRecordReader;
• preserves existing Manifest partition-column restoration when partition fields are requested.

The core change is format-neutral. It does not add Direct Bundle or writer behavior.

Tests

Added coverage for:

• changed projections not sharing cached format mappings;
• equal RowType instances reusing the existing mapping;
• physical Mosaic files containing only business columns;
• full, business-only, and partition-only projections;
• row tracking and existing-versus-future lazy reader stability.

Focused validation:

mvn -B -ntp \
  -pl paimon-common,paimon-core,paimon-mosaic -am \
  -Dtest=ColumnarRowIteratorTest,RawFileSplitReadTest,PartitionColumnsOutsidePhysicalMosaicTest \
  -Dsurefire.failIfNoSpecifiedTests=false test

• ColumnarRowIteratorTest: 1 passed
• RawFileSplitReadTest: 2 passed
• PartitionColumnsOutsidePhysicalMosaicTest: 2 passed
• Checkstyle, Spotless, Maven Enforcer, and git diff --check: passed

[JingsongLi]

+1