chore: improve ec addition

[guipublic]

Reduces the gate count for addition in cycle group

I get 37 gates instead of 41.
I improved the equality checks by one gate by removing the boolean gate.
I rewrote a division as one gate instead of 3 thanks to the quotient being not null.

[github-actions]

Changes to circuit sizes

Generated at commit: 1d763d7710d4cf932e42177b5f183b29afb4b97b, compared to commit: b09a1bbcc31ac0af5f23e7c9677ef922d5da5239

🧾 Summary (100% most significant diffs)

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
private_kernel_reset_tiny	0 ➖	0.00%	-8 ✅	-0.01%
private_kernel_reset_small	0 ➖	0.00%	-16 ✅	-0.02%
private_kernel_reset_medium	0 ➖	0.00%	-32 ✅	-0.02%
private_kernel_reset_big	0 ➖	0.00%	-64 ✅	-0.02%
private_kernel_reset	0 ➖	0.00%	-128 ✅	-0.03%
private_kernel_reset_full_inner	0 ➖	0.00%	-128 ✅	-0.03%

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Full diff report 👇

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
private_kernel_reset_tiny	35,560 (0)	0.00%	77,790 (-8)	-0.01%
private_kernel_reset_small	39,387 (0)	0.00%	104,196 (-16)	-0.02%
private_kernel_reset_medium	47,044 (0)	0.00%	157,187 (-32)	-0.02%
private_kernel_reset_big	62,353 (0)	0.00%	263,372 (-64)	-0.02%
private_kernel_reset	92,596 (0)	0.00%	474,705 (-128)	-0.03%
private_kernel_reset_full_inner	85,690 (0)	0.00%	445,025 (-128)	-0.03%

[TomAFrench]

Suggested change

	if ((!y2.is_constant() || !y1.is_constant()) && !x_diff.is_constant()) {
	lambda = field_t::from_witness(context, (y2.get_value() - y1.get_value()) / x_diff.get_value());
	field_t::evaluate_polynomial_identity(x_diff, lambda, -y2, y1);
	} else {
	lambda = (y2 - y1).divide_no_zero_check(x_diff);
	}
	if (x_diff.is_constant() || (y2.is_constant() && y1.is_constant())) {
	lambda = (y2 - y1).divide_no_zero_check(x_diff);
	} else {
	lambda = field_t::from_witness(context, (y2.get_value() - y1.get_value()) / x_diff.get_value());
	field_t::evaluate_polynomial_identity(x_diff, lambda, -y2, y1);
	}

This if condition is pretty complex and can be simplified by swapping the two branches.

[guipublic]

Done