Add IdP timeout, remaining backward compatible

[atropos112]

Hello there,

I have attempted to use Authelia with OpenID storing pbkdf2 hash in values.yaml for authelia's helm chart and then storing the secret for grist. To do this comparison Authelia can take few seconds often surpassing the 3500ms timeout window that is the default value as described here. I didn't see an env variable I could adjust this timeout with so this is the PR of me attempting to add it.

Please do note, I don't know typescript/javascript at all, the code i wrote "looks ok" to me but please do double check.