feat(explorer): squash empty folders in one line

[Dawe257]

Description

Adds a new option compact_folders to the explorer picker. When enabled, a chain of directories where each contains exactly one visible subdirectory is rendered as a single row, joining the names with /.

This is especially useful in Java projects:

src
└── main
    └── java
        └── com
            └── example
                └── App.java

After, with compact_folders = true:

src/main/java/com/example
└── App.java

Screenshots