fix: refactored log store to avoid multimaps

[Thunkar]

To avoid #9898, multimaps are no more.

This looks weird because it's taken from #9794 that does a lot more stuff (namely, processing unencrypted logs too)

[github-actions]

Changes to circuit sizes

Generated at commit: 6d142b94b09adea31fb69ce4d9bb02ede5cf671d, compared to commit: d51309954ab4a5ae1c829c86185b02c156baf3c7

🧾 Summary (100% most significant diffs)

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
private_kernel_tail_to_public	0 ➖	0.00%	+7 ❌	+0.02%
private_kernel_empty	-1 ✅	-0.16%	-1 ✅	-0.00%
rollup_base_private	0 ➖	0.00%	-7 ✅	-0.00%
private_kernel_reset	-2 ✅	-0.00%	-2 ✅	-0.00%
rollup_base_public	0 ➖	0.00%	-94 ✅	-0.00%
private_kernel_reset_4_4_4_4_4_4_4_4_1	-2 ✅	-0.01%	-3 ✅	-0.00%
private_kernel_inner	-3 ✅	-0.01%	-3 ✅	-0.01%
private_kernel_tail	-2 ✅	-0.04%	-1 ✅	-0.01%
private_kernel_init	-5 ✅	-0.02%	-5 ✅	-0.01%

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Full diff report 👇

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
private_kernel_tail_to_public	18,849 (0)	0.00%	31,297 (+7)	+0.02%
private_kernel_empty	607 (-1)	-0.16%	942,834 (-1)	-0.00%
rollup_base_private	332,869 (0)	0.00%	3,432,515 (-7)	-0.00%
private_kernel_reset	84,096 (-2)	-0.00%	618,116 (-2)	-0.00%
rollup_base_public	470,052 (0)	0.00%	3,770,556 (-94)	-0.00%
private_kernel_reset_4_4_4_4_4_4_4_4_1	32,454 (-2)	-0.01%	86,599 (-3)	-0.00%
private_kernel_inner	38,067 (-3)	-0.01%	57,508 (-3)	-0.01%
private_kernel_tail	4,490 (-2)	-0.04%	13,042 (-1)	-0.01%
private_kernel_init	21,703 (-5)	-0.02%	34,866 (-5)	-0.01%