[2.0.0-beta5] Validator: warnign if `..` operator is found

Problem/Motivation

Lets use range() function instead of the .. built-in operator because:

• .. is just syntactic sugar for the range() function. So, 1..items|length is the same as range(1, items|length), but without the possibility of adding a step
• .. doesn't' exist in Jinja and Nunjucks, but range() function does.
• Using a function will let us benefit for a check on function parameters we plan to introduce later

Proposed resolution

Raise a "Use range() function instead of `..` operator" warning if this is operator is found:

'..' => ['precedence' => 25, 'class' => RangeBinary::class, 'associativity' => ExpressionParser::OPERATOR_LEFT],

Data model changes