On Issue, "checkout topic branch" should use existing branch if already created in UI

This is similar to #4120, but not identical.

There is a feature in the UI of the website, in the right side-bar of an issue, under "Development", to create a branch for an issue.

In VS Code PR and Issue view, under "Issues > Recent Issues", when clicking on an issue then the arrow to "Start working on issue and checkout topic branch", my feature requirements are :

• if a branch has already been created for this issue, use this branch instead of creating a new one
• if creating a new branch from here, give the user to rename this branch, and attach it to the issue so that it is visible in the issue side-bar on the github website, under the "Development" section

VS Code の PR and Issue ビューにある Issues > Recent Issues のフローから開始し、「Start working on issue and checkout topic branch.」の背後にあるコマンドを追跡します。GitHub issue の Development ブランチ関連付けがどのように表現されているかを確認します。既存の issue ブランチが再利用され、新しく作成されたブランチをリネームして issue に関連付け、GitHub に表示できれば完了です。