[MNG-8084] Make the v4 api usable outside the Maven runtime

[gnodet]

First step at making the Maven 4 API usable outside a full maven process.
This PR includes:

• move Maven 4 api implementation classes from maven-core into a new maven-api-impl module
• implement native services for settings and toolchains builders, make v3 implementation wrap the new ones
• various API enhancements related to the two services above

The Maven 4 API is not completely usable outside Maven yet, but here's a working example:

        Session session = ApiRunner.createSession();

        ArtifactCoordinate coord = session.createArtifactCoordinate("org.apache.maven:maven-api-core:4.0.0-alpha-13");
        Map.Entry<Artifact, Path> res = session.resolveArtifact(coord);
        assertNotNull(res);
        assertNotNull(res.getValue());
        assertTrue(Files.exists(res.getValue()));

        Node node = session.collectDependencies(session.createDependencyCoordinate(coord));
        assertNotNull(node);
        assertEquals(8, node.getChildren().size());

[cstamas]

IIUC, this moves things out from maven-core to somewhere at line of maven-resolver-provider?

[gnodet]

IIUC, this moves things out from maven-core to somewhere at line of maven-resolver-provider?

Yes, the dependencies are:

• maven-api-core (so the whole maven api)
• maven-di (the dependency injection framework)
• maven-resolver-provider
• and obviously the resolver

The next step would be to make maven-resolver-provider and maven-model-builder built on top of the maven 4 model to make it even more lightweight.