recentworkspace.json does not update roots on application close

[ndoschek]

Bug Description:

When multiple instances of Theia are opened with different workspaces, the most recently opened workspace is written to index 0 of $USER_HOME/.theia(-ide)/recentworkspace.json. However, the order is not updated on application close.

Steps to Reproduce:

1. Open Theia with workspaceA.
2. Open a second instance with workspaceB.
3. Close workspaceB, continue working in workspaceA.
4. Close workspaceA.
5. Open the application again and observe workspaceB is opened.

This suggests the roots list is only updated on open, not on close.

Expected behaviour:

• Since workspaceA was the last closed workspace, it should appear at index 0 in recentworkspace.json, and be restored next time the application starts.

[colin-grant-work]

May be related to changes made in #16238 . At least one request to set the most recent workspace was removed there.