Gradle plugin should leverage task configuration avoidance

[DPUkyle]

For PegasusPlugin, invoking tasks.create is more heavyweight than the desirable tasks.register API. For very large projects, this new API can have a significant effect on build configuration time by lazily deferring Task object instantiation.

One caveat - the TaskContainer#register API is introduced with Gradle 4.9. Implementing it will effectively break projects who build with a lower version of Gradle when applying the pegasus plugin. If necessary, backwards-compatibility could be preserved by sampling org.gradle.util.GradleVersion#current. But even Gradle 4.9 is quite old and it's reasonable to expect consumers of the pegasus plugin to be building with Gradle 5 or higher. This could also be caught very early in the PegasusPlugin#apply method, failing gracefully and warning the user about a minimum required version.

Read more about task configuration avoidance here.