Introduce a lazy way to determine upload (runtimePush)

[omarismail94]

Add a Runtime switch that determines whether the build attempts to upload entries to the remote build cache. Unlike [org.gradle.caching.configuration.BuildCache.isPush], this flag is not part of the Gradle Configuration Cache model’s fingerprint and is only used at execution time. Keeping push = true in settings.gradle[.kts] and gating uploads with this property allows you to toggle pushing without invalidating the configuration cache