Remove usage of spaceless tag in Twig templates and fix tests

Problem/Motivation

spaceless tag has been removed in Twig 3. It is not used in Drupal 9 anymore.

Proposed resolution

Use spaceless filter instead in Drupal 8 too to help new sites become compatible with Twig 3 / Drupal 10.
https://twig.symfony.com/doc/3.x/filters/spaceless.html

Before:

{% spaceless %}

{% endspaceless %}

After:

{% apply spaceless %}

{% endapply %}

Remaining tasks

Create a patch.

User interface changes

None.