API: Adjust feature usage log format

On the advice of the Research Analyst, quote all data fields and add
slashes to escape quotes.

Change-Id: I3471475c0ae7a11398a774b1a14d023676259c04
Follows-up: Ifd640883e46f3e6c8179c63d122c704b046674ca
Merge "API: Adjust feature usage log format"