OIDC pkce timeout

[danielnginx]

Enable the ability to set the timeout for the following:

keyval_zone zone=oidc_pkce:128K timeout=90s;
keyval_zone zone=oidc_id_tokens:1M timeout=1h sync;
keyval_zone zone=oidc_access_tokens:1M timeout=1h sync;
keyval_zone zone=refresh_tokens:1M timeout=8h sync;

References

nginxinc/nginx-openid-connect#110 (comment)