[civicrm.files] token doesn't work in some cases since 5.27

Broadly there have been 2 reports 1 from gharris in mattermost and also @justinfreeman has reported issues on a site where the usage of [civicrm.files] token in the urls broke the site (likely extension related)

I proposed this https://github.com/civicrm/civicrm-core/pull/17868 as a fix but not likely to get merged

@haystack @kcristiano

@totten suggested that sites affected run the following script locally https://gist.github.com/totten/5997ff53088b159e7275f761e52f9516 and reporting the findings back

Edit by kcristiano steps to reproduce:

• Have a WP CiviCRM on a version <= 5.26.2
• use the 'legacy' files location /wp-content/plugins/files/civicrm
• use [civicrm.files] in Resource URL and directory UI screens (as these will be saved in civicrm_settings)
• Upgrade to 5.27.x

After upgrade [civicrm.files] resolves to /wp-content/uploads/civicrm

Work around is to set the Resource URLs and Directories to the legacy locations in the UI screens or in overrides in civicrm.settings.php