Promote process.env_vars to GA. This field has been stabilized and in use for some time now, so it should be promoted to GA status.

• Have you signed the contributor license agreement?  ✅
• Have you followed the contributor guidelines? ✅
• For proposing substantial changes or additions to the schema, have you reviewed the RFC process? N/A
• If submitting code/script changes, have you verified all tests pass locally using make test? ✅
• If submitting schema/fields updates, have you generated new artifacts by running make and committed those changes? ✅
• Is your pull request against main? Unless there is a good reason otherwise, we prefer pull requests against main and will backport as needed. ✅
• Have you added an entry to the CHANGELOG.next.md? ✅