Finalize paste api and drop api tweaks

Fixes #30066

This finalizes the documentPaste api. This api allows extensions to attach metadata on text copy and change how content is pasted. Some examples:

- Updating imports for pasted code
- Inserting an image as an attachment in notebooks
- Pasting files converts them to relative text paths

extensions/vscode-api-tests/package.json

@@ -17,7 +17,6 @@
     "defaultChatParticipant",
     "diffCommand",
     "documentFiltersExclusive",
-    "documentPaste",
     "editorInsets",
     "embeddings",
     "extensionRuntime",