[Feature request] Support Project Isolation

[ZacSweers]

Project isolation is coming down the pipeline in Gradle and adds new limitations

https://gradle.github.io/configuration-cache/#status_as_of_gradle_8_5

The problematic line is use of subprojects here: https://github.com/dropbox/focus/blob/main/focus-gradle-plugin/src/main/kotlin/com/dropbox/focus/FocusPlugin.kt#L71

This is part of a larger issue with this feature's limitations: https://github.com/gradle/gradle/issues/22514

[0legg]

Also, configuration cache doesn't work for createFocusSettings task.

Exception at com.dropbox.focus.CreateFocusSettingsTask.createFocusSettings(CreateFocusSettingsTask.kt:24)
org.gradle.api.InvalidUserCodeException: Invocation of 'Task.project' by task ':bolt:app-rider:createFocusSettings' at execution time is unsupported.