[mmstick]

Escapes \ and " characters in serial numbers when outputting in KDL format

Closes pop-os/cosmic-epoch#2111

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[jacobgkau]

I don't have a display that was affected by pop-os/cosmic-epoch#2111, and I don't think the team as a whole does, either, based on the comments in that issue and its duplicates. But regression testing on this update looks good with non-affected displays, both single-display and multi-display.