report: refactor JSON writer

- Support non-string entry types
- Prefer single-character writes over string writes
- Rename the state constants and adjust style to match more
  common Node.js style

PR-URL: https://github.com/nodejs/node/pull/25651


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Matheus Marchini <mat@mmarchini.me>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>