feat: Support lockfile v7

[Pavel Zwerschke (pavelzw)]

Motivation

closes #305

Changes

---

If updating documentation:

• Updated documentation in https://github.com/prefix-dev/pixi/blob/main/docs/deployment/pixi_pack.md as well

[Pavel Zwerschke (pavelzw)]

after the update we produce slightly different environment.tars:

❯ pixi exec diffoscope environment-*.tar
--- environment-new.tar
+++ environment-old.tar
├── environment.yml
│┄ Ordering differences only
│ @@ -1,20 +1,20 @@
│  channels:
│    - ./channel
│    - nodefaults
│  dependencies:
│ -  - pip=24.3.1=pyh8b19718_0
│ -  - setuptools=75.6.0=pyhff2d567_1
│ -  - tzdata=2024b=hc8b5060_0
│ -  - wheel=0.45.1=pyhd8ed1ab_1
│    - bzip2=1.0.8=h99b78c6_7
│    - ca-certificates=2024.8.30=hf0a4a13_0
│    - libexpat=2.6.4=h286801f_0
│    - libffi=3.4.2=h3422bc3_5
│    - libsqlite=3.47.0=hbaaea75_1
│    - libzlib=1.3.1=h8359307_2
│    - ncurses=6.5=h7bae524_1
│    - openssl=3.3.1=hfb2fe0b_0
│ +  - pip=24.3.1=pyh8b19718_0
│    - python=3.12.5=h30c5eda_0_cpython
│    - readline=8.2=h92ec313_1
│ +  - setuptools=75.6.0=pyhff2d567_1
│    - tk=8.6.13=h5083fa2_1
│ +  - tzdata=2024b=hc8b5060_0
│ +  - wheel=0.45.1=pyhd8ed1ab_1
│    - xz=5.2.6=h57fd34a_0