Python Launcher Gains Virtual Environment Support

The Windows installer for Python includes a launcher to locate the correct Python interpreter. However, it previously lacked virtual environment support. PEP 486 proposes making the launcher 'virtualenv aware'. This means that when no specific interpreter is given, the launcher will prioritize the currently active virtualenv, falling back to the default Python if none is active. This simplifies running Python commands within virtual environments, avoiding the need for different commands in different contexts.