test(e2e): merge single-node fee, proving, and sequencer config suites

[spalladino]

Round-2 e2e consolidation, PR 4 of 9 (single-node merges). All merges preserve every asserted behavior; no assertions dropped.

Merges (old → new)

• single-node/fees/public_payments.test.ts + single-node/fees/sponsored_payments.test.ts → folded into single-node/fees/private_payments.parallel.test.ts as two unrolled its (plain string titles — the target is .parallel). All three ran the same FeesTest+FPC fixture; the shared beforeAll gains applySponsoredFPCSetup(), which is a PXE contract registration (the SponsoredFPC is already funded at genesis via fundSponsoredFPC), not an extra tx. The folded its compute their padded-max-fee gas settings locally, matching the originals.
• single-node/proving/empty_blocks.test.ts + single-node/proving/world_state_pruning.test.ts + single-node/misc/node_block_api.test.ts → single-node/proving/default_node.test.ts: one context-default setupWithProver({}) node, one describe per former file. Ordered so world_state_pruning (needs minTxsPerBlock:0 empty checkpoints) runs before empty_blocks (raises minTxsPerBlock). node_block_api queries the genesis block, which is setup-agnostic, so it drops its former bespoke PIPELINING setup.
• single-node/sequencer/slasher_config.test.ts + single-node/sequencer/sequencer_config.test.ts → single-node/sequencer/runtime_config.test.ts: one setupBlockProducer carrying both suites' knobs (slasher inactivity config + maxL2BlockGas/manaTarget/bot account). The sequencer half keeps its syncChainTip: 'checkpointed' via explicit pxeOpts since setupBlockProducer defaults to 'proposed'.
• single-node/block-building/block_building.test.ts: the 8-it double-spend suite is now an it.each table over {firstKind, secondKind, sameBlock, expectedError} (plain file, tables safe). Filename kept so the bootstrap.sh TIMEOUT=25m override and the .test_patterns.yml entry keep applying. All other its unchanged.

Container count

• Plain-file containers: −5 (public_payments, sponsored_payments, empty_blocks, world_state_pruning, node_block_api, slasher_config, sequencer_config deleted; default_node, runtime_config added).
• .parallel per-it containers: +2 (the folded fee its), each far cheaper than the full plain-file fixture they replace.
• its: 8 double-spend its → 1 it.each × 8 rows (same coverage, one title pattern).

Folds skipped

• single-node/proving/cross_chain_public_message.test.ts stays put: it is not default-compatible (sequencerPublisherAllowInvalidStates: true, minTxsPerBlock: 1, numberOfAccounts: 1), unlike the plan's assumption.

Docs

• docs/docs-developers/docs/aztec-js/how_to_pay_fees.md: #include_code sponsored_fpc_simple path repointed to private_payments.parallel.test.ts; the docs:start/end:sponsored_fpc_simple block moved byte-identical.

Local runs

• runtime_config.test.ts: 3/3 in 140s
• default_node.test.ts: 3/3 in 183s
• block_building.test.ts: 18 passed / 1 skipped (pre-existing manual-only skip) in 564s
• private_payments.parallel.test.ts: 8/8 in 333s

Deferred

• end-to-end/README.md example command and single-node/README.md per-file blurbs still name the old files (README sweep is deferred per the round-2 plan; PR 5+ owns it).

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 1 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033FLAKED\033 (8;;http://ci.aztec-labs.com/cac25b9251c99496�cac25b9251c994968;;�): yarn-project/end-to-end/scripts/run_test.sh ha src/composed/ha/e2e_ha_full.parallel.test.ts "should produce blocks with HA coordination and attestations" (68s) (code: 0)