Fix Files node parent in pull request changes tree#8846

Eiji-Kudo wants to merge 5 commits into

microsoft:mainmicrosoft/vscode-pull-request-github:mainfrom

Eiji-Kudo:fix/8845-pr-tree-files-revealEiji-Kudo/vscode-pull-request-github:fix/8845-pr-tree-files-revealCopy head branch name to clipboard