This PR ensures that the permissions log will only store JSON-able data. I encountered this problem will building for snaps. This is unlikely, probably even impossible, to occur on develop at the moment, but the fix is cheap. It's accomplished as follows:

• Replace deep clone of JSON-RPC request and response objects in permissions log with stringification via fast-safe-stringify
• Add fast-safe-stringify as production dependency
  • It was already in our dependency graph, used by eth-rpc-errors and probably others

Additionally, makes the following related but distinct change:

• Remove safe-json-stringify from production dependencies
  • This dependency was unused. In the choice between it and fast-safe-stringify, the latter appears to be more widely used, and will remain our dependency graph regardless. Removing safe-json-stringify as a direct dependency removed it from our lockfile.