Move simple integration tests from JFR Test Framework to JUnit + Disable broken Custom War Packager integration tests

[oleg-nenashev]

This change adds some unit tests which allow testing (and profiling) Jenkinsfile Runner without a heavy Jenkinsfile Runner Test Harness framework. "Hello world" test execution takes around 8 seconds on my machine with JDK11, mostly due to the extension indexing as discussed in #241

[oleg-nenashev]

This change at least gets build to the demo stage.

The databound demo needs update of the core baseline:

[2020-05-10T00:11:21.685Z] [INFO] Scanning for projects...

[2020-05-10T00:11:24.202Z] [ERROR] [ERROR] Some problems were encountered while processing the POMs:

[2020-05-10T00:11:24.202Z] [ERROR] Non-resolvable import POM: Failure to find org.jenkins-ci.main:jenkins-bom:pom:2.150.2 in https://repo.jenkins-ci.org/public/ was cached in the local repository, resolution will not be reattempted until the update interval of repo.jenkins-ci.org has elapsed or updates are forced @ line 81, column 19

[2020-05-10T00:11:24.202Z]  @ 

I will merge this PR, because it pushes the build flow forward