feat: add ser_json_bytes mode 'hex'

[PrettyWood]

Change Summary

Add 'hex' mode to ser_json_bytes to serialize bytes as the hexadecimal string representation

Related issue number

closes #937

Checklist

• Unit tests for the changes exist
• Documentation reflects the changes where applicable
• Pydantic tests pass with this pydantic-core (except for expected changes)
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

Selected Reviewer: @dmontagu

[codecov]

Codecov Report

Merging #1016 (aa7fde4) into main (f67e25c) will decrease coverage by 0.02%.
The diff coverage is 60.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1016      +/-   ##
==========================================
- Coverage   93.08%   93.06%   -0.02%     
==========================================
  Files         106      106              
  Lines       15739    15747       +8     
  Branches       35       35              
==========================================
+ Hits        14650    14655       +5     
- Misses       1082     1085       +3     
  Partials        7        7              

Files	Coverage Δ
python/pydantic_core/core_schema.py	94.75% <100.00%> (ø)
src/serializers/config.rs	91.26% <55.55%> (-2.43%)	⬇️

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[codspeed-hq]

CodSpeed Performance Report

Merging #1016 will improve performances by 52.32%

_{Comparing PrettyWood:ser_json_bytes-hex (aa7fde4) with main (f67e25c)}

Summary

⚡ 1 improvements
✅ 139 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	PrettyWood:ser_json_bytes-hex	Change
⚡	test_decimal_from_string_core	82.2 µs	54 µs	+52.32%

[PrettyWood]

please review @davidhewitt

[adriangb]

This looks pretty straightforward to me, thanks for making it happen!