Co-Authored-By: NJoão Moreno <joao.moreno@microsoft.com>

List items should have role 'listitem'

fixes #91422

- Prefer using private fields
- Explicitly mark internal hook method and prefix them with _
- Renaming

For #77131

Renames the activation event from `onWebviewEditor` to `onCustomEditor` to be consistent with the reset of the API

For #91568

Fixes #90474

Revert "Revert commits for task quick pick changes. This fixes #90474"

This reverts commit d33663fa.