Ruby

[ruby/json] Reduce encoding benchmark size

Profiling revealed that we were spending lots of time growing the buffer.
Buffer operations is definitely something we want to optimize, but for
this specific benchmark what we're interested in is UTF-8 scanning performance.

Each iteration of the two scaning benchmark were producing 20MB of JSON,
now they only produce 5MB.

Now:

== Encoding mostly utf8 (5001001 bytes) ruby 3.4.0dev (2024-10-18T19:01:45Z master https://github.com/ruby/json/commit/7be9a333ca) +YJIT +PRISM [arm64-darwin23] Warming up -------------------------------------- json 35.000 i/100ms oj 36.000 i/100ms rapidjson 10.000 i/100ms Calculating ------------------------------------- json 359.161 (± 1.4%) i/s (2.78 ms/i) - 1.820k in 5.068542s oj 359.699 (± 0.6%) i/s (2.78 ms/i) - 1.800k in 5.004291s rapidjson 99.687 (± 2.0%) i/s (10.03 ms/i) - 500.000 in 5.017321s Comparison: json: 359.2 i/s oj: 359.7 i/s - same-ish: difference falls within error rapidjson: 99.7 i/s - 3.60x slower 

https://github.com/ruby/json/commit/1a338532d2