Multiple maven submodules that have been opened are displayed under the parent module

### Description

It is recommended that for multi-module maven projects, in the project view, open submodules are displayed under their parent module or in the top-most parent module, instead of being displayed on a level with the top-most parent module, which is very useful in multi-project-multi-module scenarios, to make it easy to quickly find the appropriate module.

### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a pull request?

No

Start in the NetBeans project view handling for multi-module Maven projects and trace how opened submodules are grouped with the top-most parent module. Define the parent-child display behavior for multi-project, multi-module scenarios and verify that the appropriate modules are easy to find.

Written by the indexing model from the issue text.