Recent Workspaces list broken with UNC paths and root of a drive

[lmcarreiro]

• VSCode Version: compiled local from master branch
• OS Version: Windows 10

Steps to Reproduce:

1. Open a folder and select the root of a partition drive
2. Open a network folder
3. Close the folder

Does this issue occur when all extensions are disabled?: Yes

Got this while I was trying to fix #48403

The was a similar problem in issue #38546

[isidorn]

@aeschli you introduced the splitName so you would be the better one to review this.
Though I do agree that path.basename and path.dirname should do the thing for the welcome page.
@chrmarti also assigning to you since you own the welcome page

Feel free to assign back to me and I will just stop using splitPath here

[lmcarreiro]

I thought about putting a .replace(/[\/\\]$/, '') in the parameter of splitPath before calling it, but I didn't like it.