{WIP} (PUP-9312) Don't fail entirely if one value is invalid

[glennsarti]

TODO

[puppetcla]

CLA signed by all contributors.

[Iristyle]

I've taken a different approach where we just specify which values we want, so that we don't bother even trying to read something like ConnectionString - see #7266. Of course, not all named values exist, so that has to be handled as well.

[glennsarti]

Closing in favour of #7266