Replace serde_json with simd_json where supported

[luizirber]

I found out the simd-json crate supports the same interface as serde_json, so it is an easy swap for potentially much better perf.

Drawbacks are only supported on x86_64, so need to keep serde_json for all other archs.

This PR also shows how spread the use of serde_json::from_reader across the codebase is, should probably consolidate into a method on signatures...

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 86.63%. Comparing base (c192268) to head (2d7b3e9).

Files	Patch %	Lines
src/core/src/ffi/signature.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #3174      +/-   ##
==========================================
- Coverage   86.66%   86.63%   -0.04%     
==========================================
  Files         136      136              
  Lines       15814    15834      +20     
  Branches     2713     2713              
==========================================
+ Hits        13705    13717      +12     
- Misses       1799     1807       +8     
  Partials      310      310              

Flag	Coverage Δ
hypothesis-py	25.36% <ø> (ø)
python	92.32% <ø> (ø)
rust	62.09% <80.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.