DAL/Node: Better handling of the DAL config

Context

Problem

The Config_file.t currently contains a dal field. This field provides an option to override the default DAL configuration, which is to be used in testnets such as dailynet/mondaynet. We need such overrides so we can use a mock SRS instead of loading the production SRS from a file.

However, this current setup has two probelms:

• Nodes in the same network can use have different values for the dal field, which may lead to a split in the network (because two nodes that use different SRS will disagree on the validity of DAL operations). This is possible because dal field is outside of the network config (blockchain_network).
• The octez-node and the dal-node can use different SRS. This is because the SRS for the dal-node is managed independently of the octez-node via a --use-unsafe-srs-for-tests flag.

Solution

• Move the dal field into the blockchain_network (and rename to dal_config). This way, nodes in the same network will agree on the dal_config field.
• Have octez-node expose the blockchain_network.dal_config value via RPC. Then, have the dal-node call this RPC to use the same dal configuration as the octez-node.

Manually testing the MR

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