Fix oversized Load TsFile piece dispatch

[Caideyipi]

Summary

Load TsFile dispatch could send a serialized LoadTsFilePieceNode larger than the receiver's dn_thrift_max_frame_size, causing the Thrift transport to reject the frame.

• Discover each receiver's frame limit and split piece payloads using the smaller sender/receiver limit, reserving 1 KiB for the RPC envelope. Cache the remote limit for the dispatcher.
• Reassemble slices in order with a buffer preallocated to the original payload size. Return specific errors for missing metadata and invalid slices.
• Keep small requests on the existing wire format, including when an older receiver does not implement frame-limit discovery.
• Clean up partial assemblies on timeout/rollback and reject EXECUTE while slices are incomplete.

Verification

• LoadTsFileDispatcherImplTest: 7 tests passed, including differently sized sender/receiver transports, multiple replicas, limit caching, legacy fallback, and discovery failure.
• LoadTsFilePieceNodeAssemblerTest: 7 tests passed, including invalid slice diagnostics and direct/read-only buffer reassembly.
• DataNodeInternalRPCServiceImplLoadTest: 1 test passed, covering all six partial metadata combinations.
• Full-reactor mvn test-compile -DskipTests passed for both EN and ZH locales.
• DataNode Checkstyle/Spotless and EN/ZH message parity checks passed.
• A local JDK 17 microbenchmark favored 8 KiB bulk copying over byte-by-byte writing for direct and read-only inputs; the bulk path is retained.

Sliced transfers require upgraded sender and receiver DataNodes; older receivers do not understand slice metadata.