[FR]: Release the source code of upload-symbols (Crashlytics tool)

### Description

1. There's an issue using `upload-symbols` on older macOS machines - https://github.com/firebase/firebase-ios-sdk/issues/13420, and as @rizafran mentioned, it might be helpful to release the source code for our inspection.
2. Currently, the `upload-symbols` is provided **only** as an executable - https://github.com/firebase/firebase-ios-sdk/blob/3a470b021c0052a258ee8db396994c2e2aad713d/Crashlytics/upload-symbols
3. To keep the existing functionality, the executable could be provided the same way. Also, there would be source code for those interested in it.

### API Proposal

_No response_

### Firebase Product(s)

Crashlytics

Start with the existing Crashlytics/upload-symbols executable and the older-macOS problem described in issue #13420. Determine how the executable is produced and distributed, then define a source release that preserves the current upload-symbols functionality. Done means the source is available for inspection alongside the existing executable.

Written by the indexing model from the issue text.