refactor(archive): Simplify archiver test suite

[spalladino]

Cleans up the archiver test suite that tested data store getters, so no L1 data is required. Also extracts common test factory methods to a separate file.

[AztecBot]

Flakey Tests

🤖 says: This CI run detected 2 tests that failed, but were tolerated due to a .test_patterns.yml entry.

\033FLAKED\033 (8;;http://ci.aztec-labs.com/6c860c6b68bf0efb�6c860c6b68bf0efb8;;�): yarn-project/end-to-end/scripts/run_test.sh web3signer src/composed/web3signer/e2e_multi_validator_node_key_store.test.ts (37s) (code: 1) (\033Santiago Palladino\033: refactor(archive): Simplify archiver test suite)
\033FLAKED\033 (8;;http://ci.aztec-labs.com/1175880eeff6b056�1175880eeff6b0568;;�):  yarn-project/end-to-end/scripts/run_test.sh simple src/e2e_epochs/epochs_invalidate_block.parallel.test.ts "proposer invalidates multiple blocks" (605s) (code: 124) group:e2e-p2p-epoch-flakes (\033Santiago Palladino\033: refactor(archive): Simplify archiver test suite)

[spalladino]

Closing in favor of #19564