Implement id_tokens support for vault access

[Hybris95]

Considered current GitLab implementation, they preconise the use of id_tokens (instead of JWT tokens) in order to authenticate to Vault.
Currently, gitlab-ci-local does not take this implementation into account.

Please check following documentation :
https://docs.gitlab.com/ee/ci/examples/authenticating-with-hashicorp-vault/

Actually, using the "id_tokens" beacon does not generate any wrapped token.

The old implementation (which is now obsolete) is also not implemented (I'm speaking of CI_JOB_JWT & CI_JOB_JWT_V1 & CI_JOB_JWT_V2) :
https://docs.gitlab.com/ee/update/deprecations.html#old-versions-of-json-web-tokens-are-deprecated