Test: Inform users that they are running a patched version

[chrmarti]

Test for #12021

• File bugs against alex
• Linux @joaomoreno
• Windows @bpasero
• OSX @sandy081

Complexity - 3

Please check in the console that you don't see any warning on startup.

The idea is simple:

• in product.json there is a checksums field.
• all the files mentioned in there will be checked
• this is not a security feature, but a user awareness feature
• our premise is that end users end up with modified bits on disk and are unaware of it
• we then spend a lot of time to debug their issues and oftentimes it turns out they don't occur in out-of-the-box versions

Please check:

• copy somewhere safe workbench.main.js and workbench.main.css
• modify either one of the files
• open a new vscode window
• you should see a popup
• the text and buttons should make sense.
• the title adds "[Unsupported]" or something like that
• the feedback widget contains two more sentences of information
• restore the safe copies, check that the message doesn't show anymore
• the More information fwlink is not yet active in the website --> ToDo: Topic on patched bits vscode-docs#607
• edit the files again
• click the don't show again, see that we don't pop up again but the title still shows unsupported