Include java21 resource folder in jdt.debug.tests

[akurtakov]

What it does

Fixes running instance main methods on Java 21

How to test

Next I-build tests are successful

Author checklist

• [x] I have thoroughly tested my changes
• [x] The change is following the coding conventions
• [x] I have signed the Eclipse Contributor Agreement (ECA)

[iloveeclipse]

Thanks Alex.