widget-api: Implement driver readStickyEvents

[BillCarsonFr]

Depends on: matrix-org/matrix-widget-api#161

Implements a new functionality to push pre-existing sticky state when a widget is loaded, to give it an accurate view of the state.
This give the current sticky events, and the ClientWidgetApi in matrix-widget-api will filter them to only give access to the types that the current widget request permissions for.

Note: We might want to ensure that the permission/capability text for org.matrix.msc4407.receive.sticky_event unlike other read capability give access to past history? (max 1h)

Next: Do a playwright test with a simple widget displaying the state it got

Checklist

• I have read through review guidelines and CONTRIBUTING.md.
• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• I have licensed the changes to Element by completing the Contributor License Agreement (CLA)