Improve scenario update script (#759)

Following #757, improves the script for generating scenario test cases
with:

- A requirements file
- Support for downloading packse scenarios from GitHub dynamically
- Running rustfmt on the generated test file
- Updating snapshots / running tests

scripts/scenarios/generate.py

@@ -1,56 +0,0 @@
-#!/usr/bin/env python3
-#
-# Generates snapshot test cases from packse scenarios.
-#
-# Usage:
-#     $ scripts/scenarios/generate.py > crates/puffin-cli/tests/pip_install_scenarios.rs
-
-try:
-    import packse
-except ImportError:
-    print("packse must be installed")
-    exit(1)
-
-
-try:
-    import chevron_blue
-except ImportError:
-    print("chevron-blue must be installed")
-    exit(1)
-
-
-import sys
-import subprocess
-import json
-from pathlib import Path
-
-__dir__ = Path(__file__).parent
-
-TEMPLATE = __dir__ / "template.mustache"
-DATA = __dir__ / "data.json"
-
-data = json.loads(
-    subprocess.check_output(
-        [
-            "packse",
-            "inspect",
-            str(packse.__development_base_path__ / "scenarios"),
-        ],
-    )
-)
-
-# Add a generated
-data["generated_by"] = f"Generated by `{' '.join(sys.argv)}`"
-
-# Add normalized names for tests
-for scenario in data["scenarios"]:
-    scenario["normalized_name"] = scenario["name"].replace("-", "_")
-
-# Drop the example scenario
-for index, scenario in enumerate(data["scenarios"]):
-    if scenario["name"] == "example":
-        data["scenarios"].pop(index)
-
-output = chevron_blue.render(template=TEMPLATE.read_text(), data=data, no_escape=True)
-
-print(output)