Make auto handling of utf8 routes deprecated

In Symfony 3.2 the handling of utf8 routes is automatic ... but this behaviour is deprecated - and became explicit in Symfony4, [ By adding this to all routes that need it "options" = { "utf8": true } ]

We can prepare for the jump to Symfony4 and Drupal9 today -- we can make our routes explicit in Drupal8

Here is the relevant Synfony documentation.

https://symfony.com/blog/new-in-symfony-3-2-unicode-routing-support

[ This was found as part of #2976394: Allow Symfony 4.4 to be installed in Drupal 8 ]