chore: export partial hash functions

[jialinli98]

Description

Problem*

closes #29

Summary*

We want to export the partial SHA-256 hash functions to the public API.

Additional Context

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: 8e8c8412c3fa02718cdea9f0e3b25dbee56da5c4, compared to commit: c4016741405af760d983b36e4dce3e28d6b74d04

🧾 Summary (10% most significant diffs)

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
test_sha256_1.json	+39 ❌	+4.31%	+51 ❌	+0.41%
test_sha256_511.json	+60 ❌	+0.64%	-1,393 ✅	-2.59%

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Full diff report 👇

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
test_sha256_1.json	944 (+39)	+4.31%	12,481 (+51)	+0.41%
test_sha256_200.json	4,212 (+56)	+1.35%	29,085 (+76)	+0.26%
test_sha256_512.json	9,250 (+64)	+0.70%	56,186 (+64)	+0.11%
test_sha256_511.json	9,365 (+60)	+0.64%	52,417 (-1,393)	-2.59%