Fix for ClassLoading Issue Post Embed Connect Starts - Java8 Only (#111)

[hrishabhg]

Description

Making the UserFunctionLoader deterministic by specifically setting the thread context class loader

Why

• ClassGraph 4.8.59 has CVE and requires upgrade to 4.8.138+
• ClassGraph v4.8.78 removed the functionality (Changes - see ClassPathFinder.java) if enabledIgnoreParentClassLoader. classLoaderHandlerRegistryEntry.findClasspathOrder(classLoader, ignoredClasspathOrder, scanSpec, classloaderHandlerLog); . This change does not impact the Java9+ (as introduction of modularisation). This change is not compatible with Java8 as breaks ksqldb test cases and potentially can impact if a customer runs Connect in embed mode (Note: in repro - we were not able to produce it when Connect runs as embed process though).

Testing done

• Local Unit/Integration Testing

Reviewer checklist

• Ensure docs are updated if necessary. (eg. if a user visible feature is being added or changed).
• Ensure relevant issues are linked (description should include text like "Fixes #")
• Do these changes have compatibility implications for rollback? If so, ensure that the ksql command version is bumped.