[FR]: Support for io.Writer Interface in Firebase Go SDK for Realtime Database Streaming

Environment
Operating System version: osx
Firebase SDK version: v4
Firebase Product: database (realtime database)
Feature Request Description
I propose adding support for the io.Writer interface in the Firebase Go SDK to allow streaming data directly from the Realtime Database to a writer (e.g., file, buffer). The current implementation requires loading the entire response into memory, which is not efficient for large data sets.

Problem
When working with large datasets in the Realtime Database, the SDK's current implementation, which loads the entire database into memory, can lead to high memory usage and potential performance issues. This limitation is particularly challenging when dealing with large data streams or when operating in resource-constrained environments.

```
func StreamDataToWriter(dbRef *db.Ref, writer io.Writer) error {
// Example implementation using the proposed feature
// ...
}

// Usage example
file, err := os.Create("output.json")
if err != nil {
// handle error
}
defer file.Close()

dbRef := client.NewRef("path/to/data")
err = StreamDataToWriter(dbRef, file)
if err != nil {
// handle error
}
```

Additional Context
This enhancement would be beneficial for applications that process large amounts of data and need to minimize memory footprint. It aligns with Go's idiomatic use of interfaces and streaming I/O operations, promoting efficiency and flexibility in handling data streams.

Start by reviewing the Realtime Database APIs around db.Ref and client.NewRef, then trace how the current implementation loads responses into memory. Define the io.Writer-facing API and its streaming behavior, and consider how errors and partial writes should be handled. Done means large database responses can be written incrementally without loading the entire response into memory.

Written by the indexing model from the issue text.