feat(go): add BlobDescriptor batch and stream readers

[XiaoHongbo-Hope]

Summary

• expose BlobDescriptor batch and lazy stream reads through Rust, C, and Go
• reuse descriptor validation, FileIO, range merging, and shared I/O limits
• preserve batch input order and return Go-owned buffers
• let table readers reuse DLF FileIO and refresh temporary data tokens

Scope

This reads serialized descriptors directly and does not require scanning a Paimon table. Static storage options are not rotated; table.NewBlobReader() retains the table's refreshing FileIO.

This PR does not add a BLOB format, StarRocks dependency, write path, or Blob View support.

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. Reader and stream Close operations are idempotent. OpenBlob is lazy and supports descriptor-relative seeks for HTTP Range responses; independent streams are not range-merged.

Validation

• Rust Blob tests: 119 passed
• C binding tests: 67 passed
• Go BlobReader/BlobStream tests and go vet passed
• DLF token rotation tests cover batch and stream reads
• read-only DLF regression E2E sought 32 KiB into a real table BLOB and returned only the requested 1 KiB
• rustfmt, clippy, and diff checks passed

The PR remains draft while the core and binding changes are prepared for review.