Integration with vscode.dev

• Add Checkout in vscode.dev command action to GHPRI view PR context menu
• Add Open on vscode.dev to desktop git branch picker

Share menu

• Add support for consolidated Share menu (vscode#172425):
  • Editor tab context menu editor/title/context/share
  • Explorer file context menu explorer/context/share
  • SCM resource context menu scm/resourceState/context/share
  • Adopt support in
    • GitHub Pull Requests
    • GitHub Repositories
    • builtin GitHub extension
• Integrate Live Share into Share menu as Share > Start Collaboration Session
• Add Copy __ link to a new editor gutter context menu contribution point (ensure no conflict with gutter breakpoints)

Link behavior

• Copy GitHub Permalink should always generate github.com permalinks links on desktop, vscode.dev, and github.dev
• Copy vscode.dev link should generate vscode.dev links and be present only on desktop and vscode.dev
• Copy github.dev link to generate github.dev links and be present only on github.dev