feat: tightly pack public logs inside blobs

[MirandaWood]

This PR removes trailing zeroes from logs appended to the blobs to save on field space.
e.g. before this PR, a public log would be appended like:

[1, 2, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

but now is appended as:

[1, 2, 3]

with a length prefix.
In ts, we add back the trailing zeroes when constructing tx effects from the blob, so if they are required there should be no issue.
Also, in some logs there are valid zeroes inside the log. The method does not remove these. e.g. a public log like:

[1, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]

is appended as:

[1, 0, 3]

then reconstructed to the original log once in ts.

[github-actions]

Changes to circuit sizes

Generated at commit: b8b57145ce94267ffae553428aa3618e9cd67b7b, compared to commit: 6c9305897c9c333791d333d332cafa352f9bbe58

🧾 Summary (100% most significant diffs)

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
rollup_base_private	+72 ❌	+0.05%	+267 ❌	+0.02%
rollup_base_public	-21,376 ✅	-24.83%	-73,721 ✅	-6.30%

---

Full diff report 👇

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
rollup_base_private	137,902 (+72)	+0.05%	1,637,626 (+267)	+0.02%
rollup_base_public	64,716 (-21,376)	-24.83%	1,095,840 (-73,721)	-6.30%

[LeilaWang]

As discussed, private logs are always padded to the fixed length, so there won't be trailing 0s.

[LeilaWang]

Can remove this TODO (and the one below) as logs will always contain valid 0s!

[LeilaWang]

This should be find_index_hint_from_end(array, |elem: T| !is_empty(elem))
Think it's more intuitive, and matches other libraries' similar functions, to find the index of the element that makes the callback return true.

[LeilaWang]

Suggested change

	let lastZeroIndex = 0;
	for (let i = this.toFields().length - 1; i >= 0; i--) {
	if (!this.toFields()[i].isZero() && lastZeroIndex == 0) {
	lastZeroIndex = i + 1;
	break;
	}
	}
	const fields = this.toFields();
	const lastNonZeroIndex = fields.findLast(f => !f.isZero());
	return fields.slice(0, lastNonZeroIndex + 1);