feat: Hugr::store_with_exts and auto-include in serde_as

[aborgna-q]

Closes #2279

This mostly expands the docs on the current behaviour, adds a Hugr::store_with_exts call to manually include extensions in the envelope, and auto-includes extra extensions in the AsStringEnvelope helper.

[codecov]

Codecov Report

Attention: Patch coverage is 80.76923% with 5 lines in your changes missing coverage. Please review.

Project coverage is 82.17%. Comparing base (ead071b) to head (fda1ccb).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
hugr-core/src/envelope/serde_with.rs	55.55%	3 Missing and 1 partial ⚠️
hugr-core/src/hugr.rs	94.11%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2280   +/-   ##
=======================================
  Coverage   82.17%   82.17%           
=======================================
  Files         239      239           
  Lines       43012    43036   +24     
  Branches    38924    38947   +23     
=======================================
+ Hits        35346    35366   +20     
- Misses       5675     5678    +3     
- Partials     1991     1992    +1     

Flag	Coverage Δ
python	85.39% <ø> (+0.05%)	⬆️
rust	81.83% <80.76%> (-0.01%)	⬇️

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[cqc-alec]

Do you understand the benchmarking failure?

[cqc-alec]

Just some typos, but the benchmarking failure looks as if it could be related?

[codspeed-hq]

CodSpeed Performance Report

Merging #2280 will improve performances by ×2.2

_{Comparing ab/serde-with-exts (fda1ccb) with main (2c8cbb9)}

Summary

⚡ 6 improvements
✅ 15 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	circuit_roundtrip/json[10]	3 ms	2.5 ms	+20.61%
⚡	circuit_roundtrip/json[1]	981.9 µs	454.5 µs	×2.2
⚡	circuit_serialize/json[0]	87.1 µs	39.1 µs	×2.2
⚡	circuit_serialize/json[10]	417.9 µs	350.1 µs	+19.36%
⚡	circuit_serialize/json[1]	142.3 µs	83.2 µs	+71.04%
⚡	simple_cfg_serialize/json	854.4 µs	445.3 µs	+91.86%

[aborgna-q]

Fixed, I wasn't setting the extra extensions in the benchmarks.

The benchmarks show a nice improvement since we no longer encode all the std extensions :)