p2deps plugin put jars into multiple source sets

[nedtwigg]

A pattern has emerged in how the p2deps plugin is used. In Solstice it's used to add one small set of jars onto the compile classpath, and then a larger set onto a testing classpath

equo-ide/solstice/build.gradle

Lines 90 to 103 in 6d698be

	into 'compileOnly', {
	p2repo "https://download.eclipse.org/eclipse/updates/${VERSION}/"
	install 'org.eclipse.ui.ide.application'
	}
	into 'testImplementation', {
	p2repo "https://download.eclipse.org/eclipse/updates/${VERSION}/"
	install 'org.eclipse.platform.ide.categoryIU'
	addFilter 'multiple-ICompilationUnit', {
	it.exclude 'org.apache.jasper.glassfish'
	}
	install 'org.eclipse.releng.java.languages.categoryIU'
	p2repo 'https://download.eclipse.org/buildship/updates/e423/releases/3.x/3.1.6.v20220511-1359/'
	install 'org.eclipse.buildship.feature.group'
	}

And in Spotless it's used to add different things into multiple compileOnly classpaths

https://github.com/diffplug/spotless/blob/bc21f833c000b4095232bf211edacd8450a7ac2d/lib-extra/build.gradle#L71-L87

But we really want to add it into the testImplementation classpath too. e.g.

p2deps {
  into ['jdtCompileOnly', 'jdtTestImplementation'], {
    p2repo 'https://download.eclipse.org/eclipse/updates/4.26/'
    install 'org.eclipse.jdt.core'
    ...

So it would be nice if we could pass a List<String> for the configuration list, instead of needing to copy the block manually.