Better structure for native sampling output

[marchdf]

Summary

This new folder structure makes it so the native sampling output (which uses particles) is natively read by typical viz programs, e.g., paraview.

Pull request type

Please check the type of change introduced:

• [x] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] Documentation content changes
• [ ] Other (please describe):

Checklist

NA, this only affects the folder structure of the native sampling output.

Additional background

Paraview can now easily load these particles up for quick visualization

Old folder structure:

post_processing
├── abl_statistics00000.txt
├── othersampling00000
│   ├── Header
│   └── Level_0
│       ├── DATA_00000
│       └── Particle_H
├── othersampling00001
│   ├── Header
│   └── Level_0
│       ├── DATA_00000
│       └── Particle_H
├── othersampling00002
│   ├── Header
│   └── Level_0
│       ├── DATA_00000
│       └── Particle_H
├── sampling00000
│   ├── Header
│   └── Level_0
│       ├── DATA_00000
│       └── Particle_H
├── sampling00001
│   ├── Header
│   └── Level_0
│       ├── DATA_00000
│       └── Particle_H
└── sampling00002
    ├── Header
    └── Level_0
        ├── DATA_00000
        └── Particle_H

New folder structure:

post_processing
├── abl_statistics00000.txt
├── othersampling00000
│   └── particles
│       ├── Header
│       └── Level_0
│           ├── DATA_00000
│           └── Particle_H
├── othersampling00001
│   └── particles
│       ├── Header
│       └── Level_0
│           ├── DATA_00000
│           └── Particle_H
├── othersampling00002
│   └── particles
│       ├── Header
│       └── Level_0
│           ├── DATA_00000
│           └── Particle_H
├── sampling00000
│   └── particles
│       ├── Header
│       └── Level_0
│           ├── DATA_00000
│           └── Particle_H
├── sampling00001
│   └── particles
│       ├── Header
│       └── Level_0
│           ├── DATA_00000
│           └── Particle_H
└── sampling00002
    └── particles
        ├── Header
        └── Level_0
            ├── DATA_00000
            └── Particle_H