Remove deprecated Twig_SimpleFilter and Twig_Extension usage

@Sutharsan, unfortunately, no. Drupal 8 used Twig 1, which didn't have this new class. But it is impossible to support Twig 3 / Drupal 10, Twig 2 / Drupal 9 and Twig 1 / Drupal 8 at the same time. The only way would be through a check if the class exists or not and to that condition to change between Twig 1/2 code, and Twig 2/3 code.

However, Drupal 8 is no longer supported, and modules should focus on supporting Drupal 10 instead of ^8 || ^9 || ^10.

In any case the patch above is missing a full class path (\Twig\TwigFilter) or a use statement.

Well, seems like this is now the Drupal 10 update issue, as such let's change it, and add the new bug I found: the \Twig_Extension is also not part of Twig 3, and has been replaced with:

+use Twig\Extension\AbstractExtension;

-class FieldValueExtension extends \Twig_Extension {
+class FieldValueExtension extends AbstractExtension {

Needs a re-roll after #3295680: Drupal Coding Standards

This is the re-roll of #11. Can't create an interdiff easily, but the only reason the patch didn't apply is that the coding standards issue fixed a double space before an '=' sign.

The patch in #11 was maintaining that error, and fixing that and removing a blank line at the start of that function were the only changes in this patch.

Further re-roll after https://git.drupalcode.org/project/twig_field_value/-/commit/925f0296df9...

Regarding #16, the proper fix should be defining that module to be part of the "Testing" package, and not specifying any core or core_version_requirement at all.

Now fixing also #16, as I described above.

Tested now with D10 as well, all green.

As to the testing package and no "core_version_requirement" it is documented here: https://www.drupal.org/node/3070687#test

Please commit this and tag a new release, since version 2.0.1 declares itself as Drupal 10 compatible, but it really isn't without these changes.