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

Beginne im Ablauf Issues > Recent Issues der VS Code-Ansicht PR and Issue und verfolge den Befehl hinter „Start working on issue and checkout topic branch.“ Überprüfe, wie die Development-Zuordnung des GitHub-Issues zu einem Branch dargestellt wird. Als erledigt gilt die Wiederverwendung eines vorhandenen Issue-Branches, während ein neu erstellter Branch umbenannt und dem Issue zur Anzeige in GitHub zugeordnet werden kann.