Allow usage of Quarkus Gradle Plugin as a custom plugin dependency

[38leinaD]

Description
It would be nice to hide some default configuration for our used quarkus version/dependecies/etc behind our own custom Gradle plugin. This is useful, because we have multiple quarkus apps managed by our team that are developed and released together; as such, we would like to be able to define the used quarkus version and some settings in a central place; i.e. a gradle plugin and not having to define the quarkus gradle plugin dependency in each project individually.

This custom gradle plugin should dependent on the quarkus gradle plugin in it's build-script to pull it in transitively:

implementation 'io.quarkus:io.quarkus.gradle.plugin:1.8.1.Final'

Our custom gradle plugin will now apply the quarkus gradle plugin:

  @Override
    public void apply(Project project) {
		project.apply plugin: 'io.quarkus'
                // add some default dependencies, etc....
    }

There should be NO direct dependency in the settings.gradle of the quarkus project like this (all should be hidden by our custom gradle plugin if possible):

pluginManagement {
    plugins {
      id 'io.quarkus' version "1.8.1.Final"
    }
}

Unfortunately, when applying this plugin and pulling it in just as a transitive dependency, the quarkusDev plugin will fail because it searches for the quarkus gradle plugin dependency just in the direct dependencies.
(https://github.com/quarkusio/quarkus/blob/master/devtools/gradle/src/main/java/io/quarkus/gradle/tasks/QuarkusDev.java#L489)

        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.lambda$run$0(DefaultPlanExecutor.java:127)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.execute(DefaultPlanExecutor.java:191)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.executeNextNode(DefaultPlanExecutor.java:182)
        at org.gradle.execution.plan.DefaultPlanExecutor$ExecutorWorker.run(DefaultPlanExecutor.java:124)
        at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:64)
        at org.gradle.internal.concurrent.ManagedExecutorImpl$1.run(ManagedExecutorImpl.java:48)
        at org.gradle.internal.concurrent.ThreadFactoryImpl$ManagedThreadRunnable.run(ThreadFactoryImpl.java:56)
Caused by: java.lang.IllegalStateException: Unable to find quarkus-gradle-plugin dependency in project ':quarkus-minimal-assembly'
        at io.quarkus.gradle.tasks.QuarkusDev.addGradlePluginDeps(QuarkusDev.java:529)
        at io.quarkus.gradle.tasks.QuarkusDev.startDev(QuarkusDev.java:314)
        ... 92 more

Implementation ideas
For such use-cases, it would be good if the quarkus gradle plugin is also search in the transitive dependencies; which might be the case if it is just pulled in by some other plugin.

[quarkusbot]

/cc @quarkusio/devtools, @glefloch