Upgrade to ocamlformat 0.26.0

Context

Manually testing the MR

A notable change is the indentation of a let or if directly inside parentheses. The non-indentation change are due to module arguments (generally small diffs) and classes (generally huge diffs).

Feedback welcome.

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