feat(go): add BlobDescriptor batch and stream readers

[XiaoHongbo-Hope]

Summary

• expose the merged Rust BlobReader and BlobStream through C and Go
• add ordered batch reads and lazy io.ReadSeekCloser streams
• let table.NewBlobReader() reuse the table FileIO, including DLF token refresh

Descriptor parsing, validation, range merging, concurrency limits, and storage I/O remain in Rust core (#762 and #763). The Go layer only manages FFI ownership and Go-friendly APIs.

Go API

reader, err := paimon.NewBlobReader(storageOptions)
reader, err := table.NewBlobReader()

values, err := reader.ReadBlobs(descriptors)
stream, err := reader.OpenBlob(descriptor) // io.ReadSeekCloser

ReadBlob delegates to ReadBlobs. Batch reads merge compatible ranges and preserve input order. Independent streams are lazy and are not merged.

Static options passed to NewBlobReader are not refreshed. table.NewBlobReader() retains the table's refreshing FileIO for DLF temporary data tokens.

Validation

• cargo test --locked -p paimon-c --lib: 71 passed
• Go BlobReader/BlobStream runtime tests: 4 passed; local table-fixture case skipped
• go vet, rustfmt, clippy, dependency report, and diff checks passed

This PR adds only the C/Go binding layer; the Rust core implementation is already merged.

[JingsongLi]

+1