OutOfMemoryError occurred when calling Utilities.splitIntoFramesg function

# OutOfMemoryError occurred when calling Utilities.splitIntoFramesg function

## Description

An OutOfMemoryError vulnerability exists in the Utilities.splitIntoFrames method in firebase-admin 9.2.0.

## Error Log

```
java.lang.OutOfMemoryError: Java heap space

at java.base/java.lang.StringLatin1.newString(StringLatin1.java:715)
at java.base/java.lang.String.substring(String.java:1879)
at com.google.firebase.database.utilities.Utilities.splitIntoFrames(Utilities.java:131)
at PoC.firebas_admin.UtilitiesFuzzerSplitIntoFrames.splitIntoFramesFuzzerTest(UtilitiesFuzzerSplitIntoFrames.java:9)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
```

## PoC
```xml

com.google.firebase
firebase-admin
9.2.0

```

```java
import org.junit.Test;
import com.google.firebase.database.utilities.*;
public class UtilitiesFuzzerSplitIntoFrames {
@Test
public void splitIntoFramesFuzzerTest() {
try {
String[] result = Utilities.splitIntoFrames("9.", 0);
} catch (Exception e) {
}
}
}
```

Utilities.java:131 の com.google.firebase.database.utilities.Utilities.splitIntoFrames から始め、入力 "9." とフレームサイズ 0 を指定して UtilitiesFuzzerSplitIntoFrames PoC を使い、報告を再現します。この入力に対する想定される処理を特定し、結果として生じる動作によって Java ヒープの枯渇が発生しなくなったことを検証します。

索引モデルが issue の本文から書いたものです。