feat: mechanics to capture conflations & replay them as test cases

[delehef]

This PR adds two feature:

• an RPC endpoint available under rollup_captureConflation, accepting a first and last block as params, and returning a JSON-encoded representation of the minimal set of information required to replay the given block range without requiring a fully-synchronized blockchain state, e.g.:

curl -X POST 'http://localhost:8545'
--data '{
   "jsonrpc":"2.0",
   "method":"rollup_captureConflation",
   "params":["296519", "296521"], "id":"1"
 }'
| jq '.result.capture' -r 
| gzip > arithmetization/src/test/resources/replays/my-test-case.json.gz

• an extension of the test framework to load a minimal state as defined above, and replay it as a unit test without requiring access to an archive of the blockchain state, through the use of the ReplaysTests.replay(String fileName) static method.

[letypequividelespoubelles]

LGTM