This change fixes the step mavenExecuteStaticCodeChecks to skip execution
if no tool is configured. Previously, the step was executed even when both
supported tools, i.e., PMD and SpotBugs were disabled.
* [refactoring] move the shell/command related interfaces into pkg/command
otherwise we are not able to use the corresponding mocks for the items contained in pkg since
these interfaces are not visible from the pkg folder
Co-authored-by: Daniel Kurzynski <daniel.kurzynski@sap.com>