In our tests, the JNI code in Netty tcNative can cause some of its
classes to be loaded using a ModifiedClassPathClassLoader. When the
wrong class loader is used, SSL-related tests fail, for example due
to the same Netty tcNative classes being loaded by two different
ClassLoders and no longer being the same. This appears to be
dependent upon the order in which tests are executed and results in
intermittent test failures.

It looks like this should be addressed in Netty tcNative 2.0.40 which
preloads all of its classes. In the meantime, this commit updates
ModifiedClassPathClassLodaer to ignore Netty tcNative classes so that
they're only ever loaded by the system class loader.

Closes gh-26749