Fix#7350 Logging/loading file in Janino Plugin causes problems when used in booJar environments

[leehaut]

Fix #7350

This change:

• Tries an external file first when a regular file exists beside the plugin jar (preserves custom Hop installation config)
• Falls back to the bundled classpath resource (/codeExclusions.xml) for Maven, Spring Boot, and nested jar deployments
• Logs ERROR only when an external file exists but cannot be parsed; missing external files no longer produce ERROR noise