Build devnet image for testing purposes

[marcelstanley]

We're not deploying the contracts in a deterministic fashion yet. That's the reason for da0c33e, which is expected to be reverted soon as part of #229.

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Testing

Please make sure to build the image:

cd build
docker buildx bake rollups-devnet --load --no-cache

Also, check if the state file has the expected size as follows:

cd /tmp
id=$(docker create cartesi/rollups-devnet:devel)
docker cp $id:/usr/share/devnet/anvil_state.json .
docker rm -v $id
ls -l anvil_state.json
cat anvil_state.json | jq >> /dev/null

Expected output (file size is 82622 bytes and there are no errors):

Successfully copied 84.5kB to /tmp/.
7e918c31f5177610196810c7eedd61212670840f5ed05e96fd4b348294645cac
-rw-r--r-- 1 username username 82622 Dec 15 16:12 anvil_state.json

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Closes #187