Summary:
In heap snapshots, it was found that really large (20 MB) strings representing network data
were being logged as part of `Systrace.beginEvent` strings from `MessageQueue` in DEV mode.
To combat this, use `JSON.stringify` with limits to keep the depth, strings, arrays, and objects
in check.
Changelog: [Internal] Change `stringifySafe` to have max limits on string size
Reviewed By: yungsters
Differential Revision: D20016501
fbshipit-source-id: e123016557bc154e4210e0b4df44360570da8016