[file-index] Support stream file index containers

[zjw1111]

Purpose

V2 file-index containers now support table writes and index rewrites when an index payload or the container exceeds 2 GiB. Previously, both production paths assembled the complete container in a ByteArrayOutputStream, so selecting V2 did not remove that size limit.

The container writer accepts payloads through writeIndex and FileIndexWriter.writeTo(OutputStream). DataFileIndexWriter and FileIndexProcessor write through a spillable output stream: small containers stay embedded in file metadata, while larger ones become independent index files. V2 records 64-bit payload positions and lengths in its footer; readers continue to accept V1 and V2. The plugin reader interface now takes a long payload length. Existing built-in index writers still serialize individual payloads as byte arrays, and V1 keeps its header-first, in-memory write behavior. V1 remains the default format.

Tests

• FileIndexFormatFormatTest: testV2TotalSizeOverTwoGiBAndLegacyBackendAtLargePosition, testV2StreamedPayloadOverInt32, and testV2CopyPayloadOverInt32 cover large positions, a single large streamed payload, and copying that payload without a large byte array. testIncrementalWriteAndCopyPayload covers V1/V2 incremental writes, and testV2RejectInvalidTailMagic covers a damaged trailer.
• DataFileIndexWriterTest: testSpillableIndexOutputStream covers the embed/spill boundary; testV2TableWriterStreamsPayloadOverTwoGiB writes a table index above 2 GiB; testV2FailedWriteDeletesPartialIndexFile checks cleanup after a failed write.
• FileIndexProcessorTest: testV2RewritesContainerOverTwoGiB rewrites a table index above 2 GiB. The map-key rewrite test also runs with V1 and V2.
• CoreOptionsTest.testFileIndexInManifestThreshold covers threshold bounds, and FileIndexPredicateCloseTest.testFileStatusFailureDoesNotOpenStream covers reader construction failure.
• FileIndexesTableTest runs embedded and external index cases with both V1 and V2.