Make rollup-template more similar to demo-rollup

[bkolad]

Description

This PR makes similar change as #1025 in demo-rollup so the two crates have the same structure.

Testing

Tests updated.

Docs

No doc changes.

[codecov]

Codecov Report

Merging #1029 (265b649) into nightly (f1ef688) will increase coverage by 0.0%.
The diff coverage is 100.0%.

Files	Coverage Δ
templates/rollup-template/src/bin/node.rs	0.0% <ø> (ø)
templates/rollup-template/src/bin/verifier.rs	0.0% <ø> (ø)
templates/rollup-template/src/da.rs	0.0% <ø> (ø)
templates/rollup-template/src/rollup/mod.rs	89.5% <ø> (ø)
templates/rollup-template/src/rollup/rpc.rs	100.0% <ø> (ø)
templates/rollup-template/stf/src/builder.rs	100.0% <100.0%> (ø)
...emplates/rollup-template/stf/src/genesis_config.rs	0.0% <ø> (ø)
templates/rollup-template/stf/src/hooks.rs	82.0% <ø> (ø)
templates/rollup-template/stf/src/runtime.rs	65.0% <ø> (ø)

... and 2 files with indirect coverage changes