Potx doesn't recognize t filters in twig 3.21

The bug seems to be introduced since:

https://github.com/twigphp/Twig/commit/42c82e1e9b88af365b15ed35cb5488f16...

Twig 3.21.0 not only broke extracting from |t filter. Potx now incorrectly extracts variable names containing a dot ({{ node.type }} becomes @node instead of @node.type).

This patch expands on #2. It fixes both issues and should work with earlier twig versions as well.

Can you put this into an MR? That way tests would run on it too :)

I've put my original patch into an MR. @volman do you have push access to my branch? If not do you want me to add your patch to the branch?