Add icon to show that class is not accessible outside package

### Description

I can agree that this feature is rather debatable, but I think it would be nice to see which classes have default access modifier by icons in projects tab.

When we work with large projects with many modules (particularly with JPMS) we want to hide many classes within package. So, when we have many classes we need to open each of them and check its access modifier. I think if there were any icon showing default access modifier it would help a lot.

### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow the Apache Software Foundation's [Code of Conduct](https://www.apache.org/foundation/policies/conduct.html)

Start by locating the Projects tab UI that lists classes and inspect how class access modifiers are represented there. The work is done when classes with default access are visibly identified by an icon without opening each class, including in projects with many modules.

Written by the indexing model from the issue text.