[2.0.0-beta5] Warning if "is iterable" test found

Problem/Motivation

Since Twig 3.11, there are 2 new tests: is sequence and is mapping.

UI Patterns 2. is supporting Drupal 10.3.4 and superior, so those tests are available:

• Drupal 9.5.1 > Twig 2.15 : https://git.drupalcode.org/project/drupal/-/blob/9.5.1/core/composer.json
• Drupal 10.3.4 > Twig 3.14 : https://git.drupalcode.org/project/drupal/-/blob/10.3.4/core/composer.json
• Drupal 11.0.3 > Twig 3.14 : https://git.drupalcode.org/project/drupal/-/blob/11.0.3/core/composer.json
• Drupal 11.1.0-dev > Twig 3.14 : https://git.drupalcode.org/project/drupal/-/blob/11.x/core/composer.json

There is no reason to use "is iterable" test in my opinion:

• On a slot, "is iterable" will always return true. A render array is a iterable, a strign is an iterable, a list of renderable is a renderable
• On a prop, we know the JSON data type of the variable: object for mapping, array for sequence

Proposed resolution

Detect is iterable test, raise this warning:

`is iterable` test is too ambiguous. Use `is sequence` or `is mapping`