Fix D2D mapping for Java class names differing from source filename

When a Java source file contains class declarations with names different
from the filename (e.g., DelombokTask.java containing class Tasks), the
compiled .class file uses the class name (Tasks.class), not the filename.

This fix:
- Extracts class/interface/enum names from Java source files during scanning
- Stores class names in extra_data["java_classes"]
- Indexes both filename-based and class-name-based paths for matching
- Enables correct D2D mapping for these edge cases

Closes #1993

Signed-off-by: Mrityunjay Raj <mr.raj.earth@gmail.com>

Author: mr-raj12