Rework ClassLoader E2E test to not rely on .version.properties file

The classloading end-to-end test makes use of the .version.properties file that is bundled with flink-runtime to ensure classloading works properly.

In particular it access the git.remote.origin.url property.

This should be changed since this property isn't stable across builds, which results in test failures when running the e2e tests against a release that was built on a different machine.

The test furthermore relies on this file also existing in the source flink-runtime module, which is a dangerous assumption as this requires flink-runtime to be built beforehand. It is also yet another instance where we navigate out of a module which should never be done.