perf(p2p): stop tx validation at the first failure where reasons are not needed

[vezenovm]

Stacked on #25221. Demonstrates the early-exit option raised in #25221 (comment), so the fee-payer balance read for an over-limit tx can be judged as its own change rather than by re-coupling the gas-limit checks.

AggregateTxValidator runs every validator and collects every reason, so a tx rejected by a free check still pays for the ones behind it. Adds AggregateTxValidator.stoppingAtFirstFailure and uses it on the RPC, req/resp and pool-migration paths, where the reason list is only logged or turned into an error string. Block building keeps the collect-all aggregate: its rejections are reported as part of block validation, so the full list is the diagnosis, and a tx reaching it is expected to pass anyway.

The saving is wider than the reported case: on req/resp a malformed tx no longer reaches proof verification.

Gossip does not benefit

LibP2PService.runValidations maps over the stage-1 record and Promise.alls it, because the peer penalty is the harshest severity across all failures. Every gossiped tx pays for every validator today and still will. So this reclaims cost on the local and pool paths, not on the adversarial one.

What it costs

Two things showed up once the tests ran, both worth weighing before this lands:

• A caller sees one reason instead of all of them. aztec-node had a test pinning [TX_ERROR_SIZE_ABOVE_LIMIT, TX_ERROR_CALLDATA_COUNT_MISMATCH] from a single tx; it now sees only the size error.
• A test targeting validator N has to satisfy validators 1 through N-1. The gas-limit matrix from fix(p2p): move gas-limit admission out of GasTxValidator #25221 was passing a tx that failed metadata, block-header and data validation on the mocked db, and only reached the gas-limit reason because the aggregate kept going. Those tests now build a tx that clears everything ahead of the gas checks, which is more faithful but couples them to the rest of the pipeline.

Tests

• AggregateTxValidator.stoppingAtFirstFailure returns the first reason and leaves later validators unrun.
• The reported case directly: an over-limit tx over RPC does not reach getPreviousValueIndex, which in this validator set is only reached through GasTxValidator's public state source. Verified red first, where the same tx also returns Insufficient fee payer balance (required=14652864, available=0).
• A tx that clears the earlier validators still gets the balance read, so the check is skipped rather than dropped.

p2p: 74 suites / 1433 tests. aztec-node server.test.ts: 82 tests.