fixDependencies IllegalArgumentException on unexpected format

Hello,

When attempting to upgrade from version 1.32.0 to 2.10.1 I started getting an `IllegalArgumentException` when calling fixDependencies.

```
Caused by: java.lang.IllegalArgumentException: List has more than one element.
at kotlin.collections.CollectionsKt___CollectionsKt.single(_Collections.kt:618)
at com.autonomousapps.internal.cash.grammar.kotlindsl.utils.DependencyExtractor.findIdentifier(DependencyExtractor.kt:377)
at com.autonomousapps.internal.cash.grammar.kotlindsl.utils.DependencyExtractor.parseDependencyDeclaration(DependencyExtractor.kt:167)
at com.autonomousapps.internal.cash.grammar.kotlindsl.utils.DependencyExtractor.collectDependencies(DependencyExtractor.kt:65)
at com.autonomousapps.internal.parse.KotlinBuildScriptDependenciesRewriter.handleDependencies(KotlinBuildScriptDependenciesRewriter.kt:118)
at com.autonomousapps.internal.parse.KotlinBuildScriptDependenciesRewriter.enterNamedBlock(KotlinBuildScriptDependenciesRewriter.kt:76)
at com.autonomousapps.internal.squareup.cash.grammar.KotlinParser$NamedBlockContext.enterRule(KotlinParser.java:1491)
at com.autonomousapps.internal.antlr.v4.runtime.tree.ParseTreeWalker.enterRule(ParseTreeWalker.java:50)
at com.autonomousapps.internal.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:33)
at com.autonomousapps.internal.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
at com.autonomousapps.internal.antlr.v4.runtime.tree.ParseTreeWalker.walk(ParseTreeWalker.java:36)
at com.autonomousapps.internal.cash.grammar.kotlindsl.parse.Parser.listener(Parser.kt:96)
at com.autonomousapps.internal.parse.KotlinBuildScriptDependenciesRewriter$Companion.of(KotlinBuildScriptDependenciesRewriter.kt:168)
at com.autonomousapps.internal.parse.BuildScriptDependenciesRewriter$Companion.of(BuildScriptDependenciesRewriter.kt:22)
at com.autonomousapps.tasks.RewriteTask.action(RewriteTask.kt:64)
```

I figured out that this is related to some custom extension functions that I was adding to the dependency block.

```
dependencies {
implementation(project(":foo").withFeature("bar"))
}

fun ProjectDependency.withFeature(feature: String): ProjectDependency = apply {
capabilities { requireFeature(feature) }
}
```

So it looks like the dependency parser might be more strict now in the newer version.

I managed to find a fairly easy workaround for my specific use case as I was typing this up
```
implementation(project(":foo")) { withFeature("bar") }
```

but it could still be good to have better error messages or improved compatibility of DependencyExtractor.

I've attached a minimum reproducer. Running `./gradlew fixDependencies --stacktrace` should reproduce

Thanks!

[Dependency Analysis fixDependencies parse crash.zip](https://github.com/user-attachments/files/18973136/Dependency.Analysis.fixDependencies.parse.crash.zip)

Start by running ./gradlew fixDependencies --stacktrace against the attached minimum reproducer. Read DependencyExtractor.kt around findIdentifier and parseDependencyDeclaration, then follow KotlinBuildScriptDependenciesRewriter.kt where dependency declarations are handled. Done means the custom extension form no longer crashes, or the failure reports the unsupported format clearly.

Written by the indexing model from the issue text.