[WIP] testing whether integration-tests as module works for plugins

[bmarwell]

Skip "default" ITs using:

mvnd clean verify  -DruntimeVersion=23.0.0.6 -Druntime=ol -Ponline-its -DskipPluginIts=true

Odd, but clean is needed b/c of the duplicate plugin descriptor.

[scottkurz]

I like the idea of bypassing the invoker:run execution (but still using invoker:install to run against the just-built-plugin). It seems like there's some work ahead though. I found a gotcha even in the LibertySettingsDirectoryTest in config-directory-it. Even though you're trying to bypass running with the invoker plugin the test Java itself is making an invoker call ! I think I fixed or bypassed it here https://github.com/OpenLiberty/ci.maven/commit/84a5a1013df14296b1954cf56c7c57fc6bf6c6c0 but maybe it shows there's a good amount of porting work potentially to take this to completion.

I like the fact that we'd no longer rely on <version>@pom.version@</version> which is unresolvable pre-substitution