[core] Add compression extension to text format data file names

[jackylee-ch]

Purpose

A text file is always written through the configured codec (AbstractTextFileWriter:44), while the reader recovers the codec from the file name alone; file.compression is not consulted on read. DataFilePathFactory.isTextFormat listed only json and csv, so file.format=text wrote zstd bytes into data-<uuid>-0.text and read them back as UTF-8 lines — garbage rows, no exception.

Format tables are unaffected (formatTableFileCompression() returns none for text); managed tables hit it with no configuration at all, since file.compression defaults to zstd.

Files already written compressed under the old name stay unreadable; this changes new writes only.

Tests

DataFilePathFactoryTest#testTextFormatCarriesTheCompressionExtension. Reverting the fix:

Expecting actual: ...-0.text
to end with: .text.zst

org.apache.paimon.io.*Test: 113 run, 0 failures.

Written with Claude Code; verification is mine.