chore(ms-config): replace fake json comments with C-style comments

Turns out that the MS Anonymizer tool actually does support json
comments, using C-style /* */ and // syntax.

I really thought I had tested that at some point.

So this commit just converts all the fake {"comment": "my text"} lines
into real comments. And adds a comment for every field skipped (i.e.
adds a comment for every field you wouldn't otherwise see because we
use an allow-list)

No functionality changes. (Except de-id might be faster now that it has
less fake rules to attempt to apply.)