How to test a GradleScanner with project dependency references

[John Rodriguez]

I've written a detector that errors when the legacy project dependency syntax is used in a Gradle build script, favoring the typesafe accessor syntax, i.e.,:

instead of

```

implementation project(":foo:bar")
```

use:

```

implementation projects.foo.bar

```

but I can't get the following test set up properly:

```

  @Test
  fun `legacy project path syntax detects error`() {
    lint()
      .files(
        gradle(
          """
          apply plugin: 'com.android.library'
          dependencies {
            implementation project(":foo:bar")
          }
          """
        ).indented()
      )
      .issues(GradleProjectPathDetector.LEGACY_PROJECT_PATH_SYNTAX)
      .run()
      .expect("") // left blank, so that a test failure will inform what to paste here
      .expectFixDiffs("") // ditto
  }

```

I tried adding a settings.gradle to declare 2 modules and an empty foo/bar/build.gradle to appease the test run, but that didn't work.

I also stepped through GradleModelMocker and its associated test, but looks like there's either no support for this at the moment, or I'm just missing something.