Sandbox, Scripts: Add rollup node temp data-dir

Context

This merge request updates the sandbox scripts to use a temporary directory for the rollup node, instead of using the default ~/.tezos-sc-rollup-node.

Manually testing the MR

• Run a sandbox node with ./src/bin_node/octez-sandbox-node.sh 1
• eval ./src/bin_client/octez-sandbox-client.sh 1
• Originate a sc rollup with ̀octez-client originate sc rollup from bootstrap1 of kind wasm_2_0_0 of type bytes with kernel "${KERNEL}"
• try octez-sc-rollup-node-alpha init operator config for ...

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR