Plugin/Michelson: run_step RPC to execute arbitrary Michelson code on arbitrary stack

Context

Stacked on !9946 (merged).

This MR adds a new RPC to call the Michelson interpreter at a low level. It takes arbitrary code and stack (in the format of the existing normalize_stack RPC).

This MR was extracted from the !4474 (merged) which adds client support for the TZT format. It is part of %Support for Michelson unit tests in TZT format but may also be useful to simplify the implementation of off-chain views in TzComet.

This MR also provides a client command to call this RPC; the syntax is octez-client run michelson code <code> on stack <stack>:

Bonus

Here is a small bash script building a Michelson REPL using the new client command (requires !9944 (merged) on which this MR is stacked):

#! /bin/bash

CLIENT='octez-client --mode mockup --base-dir /tmp/mockup'
STACK='{}'

while :
do
    read -p "> " COMMAND || exit 0
    if [ "$COMMAND" = "" ]
    then
        COMMAND='{}'
    fi
    NEWSTACK=$($CLIENT run michelson code "$COMMAND" on stack "$STACK" | head -n -2 | tail -n +2)
    if [ "$NEWSTACK" = "" ]
    then
        NEWSTACK="$STACK"
    else
        STACK="$NEWSTACK"
        echo "$STACK"
    fi
done

Manually testing the MR

$ octez-client run michelson code COMPARE on stack '{Stack_elt nat 2; Stack_elt nat 5}'
Result
  {Stack_elt int -1}
Gas remaining: 1039597.951 units remaining

$ echo '{PAIR}' > test
$ octez-client run michelson code test on stack '{Stack_elt nat 2; Stack_elt nat 5}'
Result
  {Stack_elt (pair nat nat) (Pair 2 5)}
Gas remaining: 1039597.514 units remaining

$ octez-client run michelson code FAIL on stack '{}'
At (unshown) location 3, script reached FAILWITH instruction
with Unit
Fatal error:
  error running script
$ octez-client run michelson code ADD on stack '{Stack_elt mutez 5000000000000000000; Stack_elt mutez 5000000000000000000}'
Overflowing addition of 5000000000000 tez and 5000000000000 tez
Fatal error:
  error running script

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