chore: non-deterministic array sort

[guipublic]

Description

Problem*

Resolves #4171
We have an intrinsic sort function to do sorting on numeric arrays. It allows field elements but fail with them.
At the same time we have a more generic sort_via method with works with custom ordering function but it has bad performance.

Summary*

I have rationalised the sorting functions for arrays, we now have only one which works on any type and support custom ordering functions.
The new sort function benefits from dynamic arrays and does not need sorting networks, so I was able to remove a lot of deprecated code. See below for the impact on performance.

The issue 4171 is resolved by specifying the Ord trait for array elements.

Additional Context

So we have 3 sort functions:
the new one 'ultra_sort'
the pre-ultra plonk 'array_sort'
the customisable one, 'sort_via'
With this PR, we only keep the new one 'ultra_sort'. Here how it compares with the others:

Sorting an array of 10 elements:

• Ultra sort: 99 Acir gates, 202 UltraPlonk gates
• Array sort: 235 Acir gates, 279 UltraPlonk gates
• Sort_via: 1733 Acir gates, 1867 UltraPlonk gates

Sorting an array of 100 elements:

• Ultra sort: 999 Acir gates, 1597 UltraPlonk gates
• Array sort: 6674 Acir gates, 6673 UltraPlonk gates
• Sort_via: 1524713 Acir gates, 1522136 UltraPlonk gates

Documentation*

Check one:

• No documentation needed.
• Documentation included in this PR.
• [Exceptional Case] Documentation to be submitted in a separate PR.

PR Checklist*

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[github-actions]

Changes to circuit sizes

Generated at commit: 15e34e73cdd95c265b92d5908a8dfef68a3dde19, compared to commit: fd150521a480c04ff64f84e3c1a2faf1e8394516

🧾 Summary (10% most significant diffs)

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
array_sort	-3 ✅	-8.82%	+14 ❌	+17.07%

---

Full diff report 👇

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
array_sort	31 (-3)	-8.82%	96 (+14)	+17.07%

[guipublic]

This PR also resolves #4261

[jfecher]

👍