Entrypoints `parameter_of`: new keyword for obtaining contract's (from module) parameter

Motivation and Context

In some cases it could be useful to have a way of obtaining the parameter from a module (interpreted as a contract because of @entry attributes).

Description

This MR adds a new keyword parameter_of for obtaining the parameter of a contract.

Component

• compiler
• website
• webide
• vscode-plugin
• debugger

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Performance improvement (non-breaking change that improves performance)
• None (change with no changelog)

Changelog

A new keyword is introduced: parameter_of. It can be used to obtain the type of a contract (from a module/namespace):

namespace C {
  type storage = int;

  // @entry
  const increment = (action: int, store: storage) : [list <operation>, storage] => [list([]), store + action];

  // @entry
  const decrement = (action: int, store: storage) : [list <operation>, storage] => [list([]), store - action];
};

const test_increment = (() => {
  let initial_storage = 42;
  let [taddr, _, _] = Test.originate_module(contract_of(C), initial_storage, 0 as tez);
  let contr : contract<parameter_of C> = Test.to_contract(taddr);
  let p : parameter_of C = Increment(1);
  let _ = Test.transfer_to_contract_exn(contr, p, 1 as mutez);
  return assert(Test.get_storage(taddr) == initial_storage + 1);
}) ();

As in the case of contract_of, now parameter_of becomes reserved. To still use parameter_of as an identifier, @ can be prepended.

Checklist:

• Changes follow the existing coding style (use dune @fmt to check).
• Tests for the changes have been added (for bug fixes / feature).
• Documentation has been updated.
• Changelog description has been added (if appropriate).
• Start titles under ## Changelog section with #### (if appropriate).
• There is no image or uploaded file in changelog
• Examples in changed behaviour have been added to the changelog (for breaking change / feature).