Reference other unmanaged folders as dependencies

[provide a description of the issue]

Environment

• Operating System: ANY
• JDK version: 11
• Visual Studio Code version: 1.74.2
• Java extension version: Any

Steps To Reproduce

1. Create a javaproject 0, a package and a class
2. Create other project 1 a package and a class where you use class of project 0.

Suppose I have 4 independent Java projects: project0, project1, project2, and project3.

Inside each project, I have the src folder, and inside some packages and classes. Project 1, 2, and 3 use classes from project0.

In Eclipse, I can indicate in a section that the sources of project 0 are used. When I try something similar in VScode, I go to configure the classpath of project one and see that it includes its src folder. When I add the src folder of project0, I get the following error: "The source path must be contained in the project root folder."

I can solve this by creating the .jar of project 0 and adding it to the other projects, but this is very inconvenient when making quick tests.

I know there are tools like Maven or Ant to do these things, but I would like to know if there is any way to indicate in vscode that one project uses classes from another without having to include the .jar as a dependency.

No source files, tests, or entry points are named. Start by reproducing the four-project setup and tracing the Java extension's classpath configuration, especially the source-path validation. Done would mean project1, project2, and project3 can reference project0's unmanaged sources without building a JAR or triggering the project-root error.