Refactor DateSeparator using MVVM and move to shared-components

[rbondesson]

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)

Refactor and move DateSeparator to shared-components

Summary

• Moved DateSeparator component to @element-hq/web-shared-components package as DateSeparatorView
• Replaced the JumpToDatePicker component with a compound context menu in shared components

Changes

New shared component

• Adopted the ViewModel pattern (MVVM) for the component, introducing the DateSeparatorViewSnapshot interface
• Added CSS module for styling, Storybook for visual testing and unit tests with snapshot coverage

Codebase migration

• Added DateSeparatorViewModel.tsx to element-web including unit-test
• Components in element-web now renders DateSeparatorView instead of the old component.

Test plan

• Verify date separator renders correctly in rooms
• Check Storybook stories render correctly and create new screenshots
• Run new unit tests in shared component
• Run unit tests for affected components in element-web
• Run visual tests for affected components in element-web

Tests

Before & After

• Before Refactoring

• After Refactoring

Closes element-hq/wat-internal#387

[MidhunSureshR]

Almost there 👍

[MidhunSureshR]

Thanks 🎉