Predicate parser, arithmetic parser improvements and bug fixes

[masked-rpgmaker]

Changelog:

• Sync with latest version from the archetype;
• Add some tests (yay /o/);
• Fix a bug on operator precedence where it wouldn't be updated for deeply nested operations;
• Implement game variable references into the arithmetic parser under the syntax v[<id>]. For instance:

const { expression, evaluate } = Schach.Parsing.Arithmetic;

let { parsed } = expression().run("v[5] + v[1 + v[3]]");

$gameVariables.setValue(5, 10);
$gameVariables.setValue(3, 5);

$gameVariables.setValue(6, 15);
evaluate(parsed); // < 25

$gameVariables.setValue(6, 20);
evaluate(parsed); // < 30

• Implement free variables provided at runtime under the syntax #<name>. For instance:

const { expression, evaluate } = Schach.Parsing.Arithmetic;

let { parsed } = expression().run("2^#x - #y");
evaluate(parsed, { variables: { x: 5, y: -10 } }); // < 42

• Implement functions into the arithmetic parser. Functions can be either built-in (for a complete list see evaluate.ts) or provided at runtime. Runtime functions override the built-in ones. For instance:

const { expression, evaluate } = Schach.Parsing.Arithmetic;

let { parsed } = expression().run("max(sqrt(100), f(#x))"); // max and sqrt are built-in

evaluate(parsed, {
  variables: { x: 5 },
  functions: { f: n => 40 * n }
});
// < 200

Related issues:

• Resolves Implement predicate parser #6 by adding a predicate parser to parser/text/util;
• Resolves Implement constants and free variables into the arithmetic parser #3 by adding free variables to the arithmetic parser (constants have not been implemented, as variables should be sufficient);
• Resolves Implement functions into the arithmetic parser #2 by adding function calls to the arithmetic parser;
• Resolves Generalize arithmetic parser to access game variables #1 by adding game variable references to the arithmetic parser.