Fix contrast.appname
The -Dcontrast.appname property is deprecated, we should change them to -Dcontrast.standalone.appname or -Dcontrast.override.appname, whichever is correct for the situation. I guessed which property would work but someone with more experience with these frameworks should verify my suggestions are correct.
@sourabhkatti Is this ready to go? @gilday is a reviewer. I am, too. Looks like no one signed off yet, but we'd like to clean up this PR, if possible. Copying @terra4383
We're inconsistently using "standalone" and "override", and we're using the legacy property names instead of the new names. We should always use the new, standalone property. As a system property, it is -Dcontrast.agent.java.standalone_app_name