Protobuf plugin causes eager task configuration

[This line uses `all` on a task collection](https://github.com/google/protobuf-gradle-plugin/blob/master/src/main/groovy/com/google/protobuf/gradle/ProtobufPlugin.groovy#L160) which causes the tasks to be eagerly configured. Here is the section in the documentation which explains the API which should be avoided and its replacement: https://docs.gradle.org/current/userguide/task_configuration_avoidance.html#sec:old_vs_new_configuration_api_overview

Here is the line in the Protobuf Gradle Plugin which is causing eager task configuration. The simplest fix would be to remove `.all()`.
https://github.com/google/protobuf-gradle-plugin/blob/master/src/main/groovy/com/google/protobuf/gradle/ProtobufPlugin.groovy#L160