Add support for embedded object extractor

[antony-liu]

#60519 - Extractor for *SSF embeddings
#60520 - Provide *SSF functionality via Common SS
#60521 - Enable nested XSSF GroupShapes and fix calculation of Client-/ChildAnchor
#60586 - Support embedding OLE1.0 package in XSSF / SS Common

[Copilot]

Pull Request Overview

This PR adds comprehensive support for embedded object extraction in XSSF/OOXML format spreadsheets. The changes enable creation, reading, and extraction of OLE packages and embedded objects within Excel files, addressing several issues related to SSF embeddings and XSSF GroupShapes functionality.

Key Changes:

• Added embedded object extractor functionality with new EmbeddedExtractor and EmbeddedData classes
• Implemented OLE package embedding support in XSSFWorkbook with AddOlePackage method
• Enhanced drawing and shape handling with improved generic type safety using IDrawing

Reviewed Changes

Copilot reviewed 63 out of 66 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
ooxml/XSSF/UserModel/XSSFObjectData.cs	New class implementing IObjectData for XSSF embedded objects
ooxml/XSSF/Extractor/EmbeddedExtractor.cs	New extractor class for identifying and extracting embedded documents
ooxml/XSSF/Extractor/EmbeddedData.cs	New data container class for embedded object information
main/SS/UserModel/IObjectData.cs	New interface defining common OLE shape behavior
ooxml/XSSF/UserModel/XSSFWorkbook.cs	Added AddOlePackage method for embedding OLE objects
multiple test files	Updated IDrawing type signatures to use generic IDrawing
OpenXmlFormats classes	Enhanced XML schema support for OLE objects and drawing elements

Comments suppressed due to low confidence (2)

testcases/ooxml/XSSF/SXSSFITestDataProvider.cs:28

• Separate the using statements onto different lines for better readability and consistency with coding standards.

    using NPOI.XSSF.UserModel;

testcases/ooxml/XSSF/SXSSFITestDataProvider.cs:34

• The [TestFixture] attribute is removed but this appears to be a test class. Verify that test discovery still works correctly without this attribute.

     */

[tonyqus]

LGTM