Symfony version(s) affected: 5.1.8

Description
When using an environment variable (e.g. %env(CDN_MANIFEST_PATH)%) the asset library does not detect this is a remote absolute URL and returns an error saying "Asset manifest file htts://yourcdnlink.com/manifest.json" does not exist. So Symfony is aware of the variable (as it renders the full real path) but yet it says it doesn't exist.

How to reproduce

• Use Symfony 5.1.8
• Specify json_manifest_path to be an environment variable and check that it exists
• Configure your assets: section under framework.yml

    assets:
      base_urls:
        - '%env(CDN_DOMAIN)%'
      json_manifest_path: '%env(CDN_MANIFEST_PATH)%' // resolves to https://static.ourdomain.com/manifest.json

• Observe error being thrown An exception has been thrown during the rendering of a template ("Asset manifest file "https://static.ourdomain.com/manifest.json" does not exist.").

If I replace the configuration with hardcoded domains:

    assets:
      base_urls:
        - '%env(CDN_DOMAIN)%'
      json_manifest_path: 'https://static.ourdomain.com/manifest.json'

It works correctly