Proto: remove fold_right from environment

Context

This MR removes the fold_right iterator on lists and its variants from the v9 version of the environment. The few uses of fold_right in the Alpha protocol are rewritten to rev + fold_left.

Manually testing the MR

This MR should have no semantic effect so there is not much to test manually and existing automatic tests should continue to run. It may have a small impact on perf (and so on gas benchmarks) but I would be surprised if they are measurable.

Suggested reviewers: @raphael-proust for the environment, @MarcBeunardeau for Sapling storage, @mbouaziz for parse_data and script patching.

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