json2 perf: encode faster than cJSON

[enghitalo]

json2 became 2x or 3x faster in -prod. In some cases, more faster than cJSON.

Even after array_push_many fix PR

Before / Now

MAX_ITERATIONS=100_000 ./v -prod crun vlib/v/tests/bench/bench_json_vs_json2.v

🤖[deprecated] Generated by Copilot at d32ffe3

Refactor the JSON encoder in vlib/x/json2 to use byte buffers and unsafe operations for faster and more efficient encoding. Extract the encoder code to a separate file encoder.v.

🤖[deprecated] Generated by Copilot at d32ffe3

• Remove unused imports of io and strings modules from vlib/x/json2/encoder.v (link)
• Change constants for JSON tokens and characters from byte arrays to strings or single bytes, to simplify encoding and avoid conversions and allocations (link)
• Refactor encoder methods to use byte buffers ([]u8) instead of writers (io.Writer) as arguments, to improve performance and memory efficiency by using pre-allocated buffers instead of writers that may allocate memory on each write operation (link, link, link, link, link, link, link, link, link, link, link, link, link, link, link, link)
• Use unsafe operations to copy bytes from string representations of values to byte buffers, instead of converting them to byte arrays and writing them, to avoid unnecessary allocations and conversions (link, link, link, link, link, link, link, link)
• Use string literals instead of calling str() method for booleans, to avoid memory allocation (link, link, link, link, link, link, link)
• Change encoding logic for unicode escape sequences to use a for loop instead of an unsafe operation, to avoid potential buffer overflow issues (link)
• Remove unused import of strings module from vlib/x/json2/json2.v (link)
• Change json_str and encode_array methods to use byte buffers instead of string builders, and to free buffers instead of builders, for the same reasons as above (link, link)
• Change file name from vlib/x/json2/json2.v to vlib/x/json2/encoder.v to reflect the refactoring of the encoder module (link, link)

[enghitalo]

I think the fail is not related

[spytheman]

Excellent work.