Update `/api/v4/jobs/request` endpoint to include CI secrets
configuration if job has any and the feature is available.

Inject Vault server configuration details to CI secrets API response
when runner is requesting a job. Server details are currently fetched
from CI variables, this will be moved to DB and UI later.

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/28321
and https://gitlab.com/gitlab-org/gitlab/-/issues/218746.