Change the logging level for plugin messages

We should update our `println` messages to use proper log levels so they don't show up for every type of build. The most important one is the `Checking whether `configure` binary is present` [message](https://github.com/Automattic/configure/blob/trunk/gradle-plugin/configure/src/main/kotlin/com/automattic/android/configure/ConfigurePlugin.kt#L56) which shows up for even quiet (`-q`) builds.

https://docs.gradle.org/current/userguide/logging.html

Start with gradle-plugin/configure/src/main/kotlin/com/automattic/android/configure/ConfigurePlugin.kt at line 56, then inspect the other println messages in that file. Read Gradle's logging documentation to identify suitable log levels. Done means plugin messages use appropriate levels and the configure-binary message no longer appears during quiet (-q) builds.

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