Jstzd: serialize rollup config

[ryutamago]

Context

serialzie rollup config

Description

serialize the rollup config and return as part of the config endpoint

Manually testing the PR

add integration test to jstzd
add unit test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 48.16%. Comparing base (4fed084) to head (909db37).
Report is 1 commits behind head on main.

Files with missing lines	Coverage Δ
crates/jstzd/src/task/jstzd.rs	75.08% <ø> (ø)
crates/octez/src/async/rollup.rs	95.81% <100.00%> (+0.81%)	⬆️

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