Read Gradle project/build dirs in config cache compatible way

[DSteve595]

With this and the changes in utopia-rise/kotlin-preprocessors#4, Gradle Configuration Cache can be enabled for downstream projects, which should give a nice speed boost since the same task is run over and over again during development.

This does not yet enable the config cache in the template project. Need to bring in that kotlin-preprocessors change first.

[Copilot]

Pull Request Overview

This PR refactors the generateGdIgnoreFilesTask to be compatible with Gradle Configuration Cache by moving project and build directory access to configuration-time providers instead of execution-time access.

• Replaces execution-time project property access with configuration-time providers
• Moves plugin existence check from doFirst to onlyIf condition
• Uses Gradle's layout providers for directory access instead of direct property access

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