Implement support for `id_tokens` setups

This change set implements support to configure `id_tokens` in a
somewhat user-friendly way. Due to the lacking support of map nodes as
input values multiple inputs are needed to configure it's support.

Limitation: https://gitlab.com/gitlab-org/gitlab/-/issues/452451

Closes https://gitlab.com/components/opentofu/-/issues/49

Changelog: added