Compute local repository and artifact paths without a plugin

[slachiewicz]

The only ExecutorTool, ToolboxExecutorTool, answers localRepository(), artifactPath() and metadataPath() by running eu.maveniverse.maven.plugins:toolbox through the Maven under test, so every consumer that needs an artifact path resolves a non-ASF plugin into its test local repository (#44). This is A7 in #49, and the base that the planned test-support module (T1) builds verifyArtifact* and deleteArtifacts on.

DefaultExecutorTool computes the same answers without running Maven:

• Local repository, in order: a -Dmaven.repo.local= argument of the request (the last one wins, also as -D maven.repo.local=…), the same in .mvn/maven.config, the request's maven.repo.local JVM system property, this JVM's maven.repo.local, <localRepository> of the user settings (-s/--settings, else ~/.m2/settings.xml, with ${user.home}, ${env.X} and system properties interpolated), of the global settings (-gs, else conf/settings.xml when the tool is given the installation), and finally ~/.m2/repository of the request's user home. A relative path is resolved against the request's working directory.
• Paths, relative to the local repository like the toolbox ones, in the default layout of Resolver's enhanced local repository manager: G:A[:E[:C]]:V artifacts, including the base-version directory of timestamped snapshots, and [G]:[A]:[V]:[type] metadata with -local or -<repositoryId> inserted into the file name.
• dump() needs the Maven under test, so it throws; ToolboxExecutorTool stays for that and as the authoritative provider when a split repository, a custom layout or settings profiles matter. The class Javadoc says so.

Tests:

• DefaultExecutorToolTest: 12 unit tests for the lookup order and the layout, no Maven needed.
• DefaultExecutorToolMatchesToolboxTest: runs both tools on Maven 3 and Maven 4 and asserts the same local repository, artifact paths (jar, pom, classifier, snapshot, timestamped snapshot, each installed and from a remote) and metadata paths (group, artifact, version level, local and remote). It caught one difference while writing this: an installed timestamped snapshot is named after its base version, a downloaded one keeps the timestamp.
• mvn verify passes for the whole reactor.

module-info gains requires java.xml for reading settings. The class is @since 1.1.0, the target #49 gives A7.

Closes #44

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