fix: handle sequencer building block mid-synch

[alexghr]

This PR fixes a race condition in the sequencer that would happen in e2e tests (or sandbox, basically anywhere we warp time because of auto mine) where the sequencer would not handle a block being synchronized in the middle of block production.

This PR merges getting the chain tip with checking if its components are synchronized. This way it at least will fail at canProposeAtTime since the provided archive might be old.

Thanks @spalladino and @LHerskind for help debugging this one :)

[github-actions]

Changes to public function bytecode sizes

Generated at commit: ca38846cd95def1cdfeed03c7f539f4838fbade8, compared to commit: 2fd08babea610f97d63adcea5630cfd3065fd3a8

🧾 Summary (100% most significant diffs)

Program	Bytecode size in bytes (+/-)	%
AvmTest::public_dispatch	-4 ✅	-0.01%
AvmTest::bulk_testing	-4 ✅	-0.02%
TokenBridge::public_dispatch	-4 ✅	-0.02%
Test::consume_message_from_arbitrary_sender_public	-4 ✅	-0.05%
AppSubscription::public_dispatch	-4 ✅	-0.10%
AppSubscription::constructor	-4 ✅	-0.13%
AvmTest::variable_base_msm	-16 ✅	-6.96%

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Full diff report 👇

Program	Bytecode size in bytes (+/-)	%
AvmTest::public_dispatch	69,677 (-4)	-0.01%
AvmTest::bulk_testing	22,134 (-4)	-0.02%
TokenBridge::public_dispatch	21,090 (-4)	-0.02%
Test::consume_message_from_arbitrary_sender_public	7,776 (-4)	-0.05%
AppSubscription::public_dispatch	4,206 (-4)	-0.10%
AppSubscription::constructor	3,062 (-4)	-0.13%
AvmTest::variable_base_msm	214 (-16)	-6.96%

[github-actions]

Changes to circuit sizes

Generated at commit: ca38846cd95def1cdfeed03c7f539f4838fbade8, compared to commit: 2fd08babea610f97d63adcea5630cfd3065fd3a8

🧾 Summary (100% most significant diffs)

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
rollup_base_private	+20 ❌	+0.01%	+19 ❌	+0.00%
rollup_base_public	+20 ❌	+0.01%	+20 ❌	+0.00%

---

Full diff report 👇

Program	ACIR opcodes (+/-)	%	Circuit size (+/-)	%
rollup_base_private	137,856 (+20)	+0.01%	1,775,166 (+19)	+0.00%
rollup_base_public	357,075 (+20)	+0.01%	3,167,366 (+20)	+0.00%