Tezt/Lib: Extend tezt Client.t with an optional dal_node field

Stacked on !14172 (merged)

What

This MR extends the Client.t with a dal_node : Dal_node.t option field.

Why

The dal_node not being included in Client.t requires passing it through all the functions because it is needed for the Client.bake_for function. The following commit is an example of such propagation:

!14049 (7379cc4e)

In this example, the only goal of having the dal_node in the arguments of the functions is to provide it to the bake_for function.

How

This MR extends the Client.t with a dal_node : Dal_node.t option field. The Client.spawn_command function on which relies Client.bake_for now uses the client's Dal node to generate the CLI argument --dal-node and not only on the ?dal_node given as a parameter (!14169 (9d2685bf)).

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