Reduces memory requirements in JSON parser and adds bytes/s and peak memory usage to benchmarks

[elstehle]

Description

This PR reduces memory requirements in the new nested JSON parser and adds bytes_per_second and peak_memory_usage usage to benchmarks

Checklist

• [x] I am familiar with the Contributing Guidelines.
• [x] New or existing tests cover these changes.
• [x] The documentation is up to date with these changes.