RTDB: calling `get()` on a path where a parent path is already subscribed to, will return the entire cached parent data rather than the data for the requested path

### Description

`getData:` in `FRepo.m` calls out to `getServerValue:` in `FSyncTree.m`.
In here we find a sync point for the synchronized parent node - we create a view representing this parent sync point and then return `[view completeEventCache];` - thereby disregarding that we are in fact only interested in the child node.

It seems to me like we ought to be returning `[view completeEventCacheFor: relativePath]` where the relativePath must then be stored from the iteration through the `syncPointTree`.

I will also create a PR for a fix.

### Reproducing the issue

In an RTDB project, create a structure like:

```
"cashiers": {
"a": { "name": "Test" },
"b": { "name": "Test2"}
}
```
In the app, subscribe to "/cashiers"
Then later do a `get` on "/cashiers/a"
Notice that this returns the entire 'cashiers' node rather than the expected 'cashiers/a' node.

### Firebase SDK Version

10.18.0

### Xcode Version

15.0

### Installation Method

Swift Package Manager

### Firebase Product(s)

Database

### Targeted Platforms

iOS

### Relevant Log Output

_No response_

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