PERFORMANCE: do not use MavenInvoker inside the plugin

[danglotb]

Currently, we run the instrumentation and the tests using MavenInvoker, which call maven goals.

It must have a way to attach specific goals to our own goal/plugin.

[vmassol]

Idea: call a plugin from inside your mojo. Here's how we do it on XWiki:

https://github.com/xwiki/xwiki-commons/blob/433f37885bf1941540542714ca24b3391ea6cf36/xwiki-commons-tools/xwiki-commons-tool-xar/xwiki-commons-tool-xar-plugin/pom.xml

and

https://github.com/xwiki/xwiki-commons/blob/71bbc482c5901baa61902511be5b6ed84b29b902/xwiki-commons-tools/xwiki-commons-tool-xar/xwiki-commons-tool-xar-plugin/src/main/java/org/xwiki/tool/xar/AbstractVerifyMojo.java#L365