Add Threaded text HLAPIs and Node/Text iteration HLAPIs

[vamshich13]

This PR introduces new HLAPIs for text handling and enhances existing nodes with new accessors to get allDescendants and allTextContent.

• ThreadedText related features (Experimental):

  • Editor.createThreadedText() can be used to create a ThreadedTextNode.
  • Updated ThreadedTextContentModel: The existing content model was updated to properly support the new threaded text implementation. See ThreadedTextContentModel.frames.
  • New ThreadedTextList Class: Adds a new class to represent an ordered list of ThreadedTextNode objects, creating a single, continuous text story across multiple frames.

• New Accessors on Nodes (Experimental):

  • allDescendants: A new accessor added to PageNode and VisualNode that returns a flattened, read-only list of all descendant nodes within the container.
  • allTextContent: A new accessor added to PageNode and VisualNode that returns a flattened, read-only list of TextContent instances from all text-based nodes within the container.

• New Interfaces Added:

  • TextContent: Documents the new TextContent interface.
  • TextFrameAreaGeometry: Documents the new TextFrameAreaGeometry interface.

Related Issue

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[undavide]

LGTM! Added the changelogs.