test.py: replace requirements.txt + inline script w/ pyproject.toml and uv.lock

This ensures that the correct `scan-build`/`intercept-build` version is active
while running `test.py`.  This is what was causing local errors testing `curl`,
as the wrong `intercept-build` was creating duplicate compile commands,
which `c2rust transpile` dropped with a warning, but hidden since `test.py` hides that.

Author: kkysen

pyproject.toml

@@ -0,0 +1,10 @@
+[project]
+name = "c2rust-testsuite"
+version = "0.21.0"
+requires-python = ">=3.15"
+dependencies = [
+    "distro>=1.9.0",
+    "jinja2>=3.1.6",
+    "pyyaml>=6.0.3",
+    "scan-build>=2.0.20",
+]

requirements.txt

@@ -1,14 +1,4 @@
-#!/usr/bin/env -S uv --quiet run
-# /// script
-# requires-python = ">=3.12"
-# dependencies = [
-#   "distro",
-#   "jinja2",
-#   "pyyaml",
-# ]
-# ///
-
-#!/usr/bin/env python3
+#!/usr/bin/env -S uv run
 
 import argparse