[BUG] utils.json.find_json takes up too much time

[agraul]

Description
The current implementation of utils.json.find_json has multiplicative big-O complexity and takes a lot of time when the input is large.

Setup
Install Salt in any way.

Steps to Reproduce the behavior
Import and run utils.json.find_json with large string (e.g. a few MB).

Expected behavior
Python object reflecting the JSON input or a ValueError if the input is invalid in less than a second.