Add support for embedded Python on Windows (#3161)

## Summary

References:
-
cad550030a/src/virtualenv/create/via_global_ref/builtin/cpython/cpython3.py (L58-L68)
- https://github.com/pypa/virtualenv/pull/2353
- https://github.com/pypa/virtualenv/issues/2368

Closes https://github.com/astral-sh/uv/issues/1656.

scripts/check_embedded_python.py

@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+
+"""Install `pylint` and `numpy` into an embedded Python."""
+
+import argparse
+import logging
+import os
+import subprocess
+import sys
+import tempfile
+
+
+if __name__ == "__main__":
+    logging.basicConfig(level=logging.INFO, format="%(levelname)s: %(message)s")
+
+    parser = argparse.ArgumentParser(
+        description="Check an embedded Python interpreter."
+    )
+    parser.add_argument("--uv", help="Path to a uv binary.")
+    args = parser.parse_args()
+
+    uv: str = os.path.abspath(args.uv) if args.uv else "uv"
+
+    # Create a temporary directory.
+    with tempfile.TemporaryDirectory() as temp_dir:
+        # Create a virtual environment with `uv`.
+        logging.info("Creating virtual environment with `uv`...")
+        subprocess.run(
+            [uv, "venv", ".venv", "--seed", "--python", sys.executable],
+            cwd=temp_dir,
+            check=True,
+        )
+
+        if os.name == "nt":
+            executable = os.path.join(temp_dir, ".venv", "Scripts", "python.exe")
+        else:
+            executable = os.path.join(temp_dir, ".venv", "bin", "python")
+
+        logging.info("Querying virtual environment...")
+        subprocess.run(
+            [executable, "--version"],
+            cwd=temp_dir,
+            check=True,
+        )
+
+        logging.info("Installing into `uv` virtual environment...")
+
+        # Disable the `CONDA_PREFIX` and `VIRTUAL_ENV` environment variables, so that
+        # we only rely on virtual environment discovery via the `.venv` directory.
+        # Our "system Python" here might itself be a Conda environment!
+        env = os.environ.copy()
+        env["CONDA_PREFIX"] = ""
+        env["VIRTUAL_ENV"] = ""
+
+        # Install, verify, and uninstall a few packages.
+        for package in ["pylint", "numpy"]:
+            # Install the package.
+            logging.info(
+                f"Installing the package `{package}` into the virtual environment..."
+            )
+            subprocess.run(
+                [uv, "pip", "install", package, "--verbose"],
+                cwd=temp_dir,
+                check=True,
+                env=env,
+            )
+
+            # Ensure that the package is installed in the virtual environment.
+            logging.info(f"Checking that `{package}` is installed.")
+            code = subprocess.run(
+                [executable, "-c", f"import {package}"],
+                cwd=temp_dir,
+            )
+            if code.returncode != 0:
+                raise Exception(
+                    f"The package `{package}` isn't installed in the virtual environment."
+                )
+
+            # Uninstall the package.
+            logging.info(f"Uninstalling the package `{package}`.")
+            subprocess.run(
+                [uv, "pip", "uninstall", package, "--verbose"],
+                cwd=temp_dir,
+                check=True,
+                env=env,
+            )
+
+            # Ensure that the package isn't installed in the virtual environment.
+            logging.info(f"Checking that `{package}` isn't installed.")
+            code = subprocess.run(
+                [executable, "-m", "pip", "show", package],
+                cwd=temp_dir,
+            )
+            if code.returncode == 0:
+                raise Exception(
+                    f"The package `{package}` is installed in the virtual environment (but shouldn't be)."
+                )