Support node 24 on GCF Gen1 (for Authentication function triggers)

### Related issues

Yes, this is a new instance of #1653, but for for node v24 instead of v22.

### [REQUIRED] Version info

**node: v24.12.0**

**firebase-functions: 7.0.3**

**firebase-tools: 15.2.1**

**firebase-admin: 13.6.0**

### [REQUIRED] Test case

Not applicable.

### [REQUIRED] Steps to reproduce

1. Create a Firebase Authentication trigger function, which is only available on Firebase Functions v1 (as documented in https://firebase.google.com/docs/functions/1st-gen/auth-events)
2. Have an engine specifier of >=24 in your function's `package.json`
3. Try to deploy said function, get the error: `Runtime "nodejs24" is not supported on GCF Gen1 for function [your function name]`

### [REQUIRED] Expected behavior

I want to use a single node version in my Firebase project, and I would like it to be the latest active LTS node version.

### [REQUIRED] Actual behavior

Error: `Runtime "nodejs24" is not supported on GCF Gen1 for function [your function name]`

Firebase both pushes users to migrate to v2 functions (which support Node v24), and at the same time it does not make Authentication triggers available on v2 (and/or: does not keep the Node engine support in GCF Gen1 functions aligned with Gen2). This makes deployments inconvenient and messy.

### Were you able to successfully deploy your functions?

No.

Start by tracing the deployment runtime validation for GCF Gen1 authentication triggers and compare its handling of Node 22 with the reported Node 24 case. Reproduce the deployment using the versions and steps in the issue, then verify that a Gen1 authentication trigger with a Node 24 engine specifier deploys successfully.

Written by the indexing model from the issue text.