Checkstyle config is broken

[jmalkin]

When running checkstyle, there are two issues:

• suppressions replies on undefined variable ${config_loc}
• There is an exception: Caused by: java.lang.IllegalArgumentException: 'other' is different type of Path

I was able to remedy these to where I can now run it as
java -Dconfig_loc=tools -jar /opt/homebrew/Cellar/checkstyle/10.13.0/libexec/checkstyle-10.13.0-all.jar -c tools/SketchesCheckstyle.xml src
but even that required modifying the SketchesCheckstyle.xml to add a path to Checker's basedir in the config: https://github.com/apache/datasketches-java/blob/master/tools/SketchesCheckstyle.xml#L39

Maybe this runs in specific IDEs as-is, but we need to make sure we're not exploiting quirks of an IDE if we expect people to run this routinely.

[jmalkin]

Removing that basedir line entirely might work for that part, but doesn't solve the missing ${config_loc} issue.