[python] Support OSS blob presigned URLs

[XiaoHongbo-Hope]

Purpose

Add the PyPaimon counterpart of the Java OSS BLOB presigning API introduced in #8832.

This change:

• adds Blob.to_presigned_url(file_io, table_root, validity) and a FileIO extension point;
• materializes the exact descriptor byte range in OSS with the Java-compatible object key, content type, and descriptor fingerprint metadata;
• reuses valid materialized objects and creates a fresh V4-signed GET URL;
• preserves configured OSS server-side encryption for empty and multipart materialized objects, and rejects cached objects with incompatible encryption metadata;
• supports both standard OSS URIs and legacy credential URIs without treating the legacy bucket path segment as part of the object key;
• supports static credentials and STS credentials supplied by DLF REST catalogs;
• forwards the operation through resolving, caching, and REST token FileIO wrappers;
• validates table ownership, ranges, validity, HTTPS endpoints, and the generated URL target;
• adds a copy-paste DLF quick start covering catalog configuration, table creation, MP4 BLOB writes, descriptor reads, presigning, ECS roles, and a Model Studio video_url request.

Tests

• 422 passed, 15 skipped, 61 subtests passed across the new tests and related BLOB/FileIO suites.
• AES256 and KMS unit coverage verifies multipart initialization, zero-length uploads, cache rejection/reuse, and legacy URI object keys.
• Flake8 and git diff --check passed for all changed Python files.
• Docusaurus production build passed, including REST OpenAPI validation.
• Ran an AES256 integration test against a real DLF catalog: created a table, wrote a 1 MiB BLOB, fetched the signed URL with HTTP 200, verified the returned bytes and x-oss-server-side-encryption: AES256, and removed the table.
• Previously ran the Python block extracted from the quick start against a real DLF catalog: created the table, wrote a 1.1 MB MP4, read its descriptor, fetched the signed URL with HTTP 200, and received HTTP 200 from DashScope qwen3.8-flash.
• Removed the integration-test DLF tables, materialized OSS objects, and local files.