Implement PEP 773

[zooba]

Feature or enhancement

For tracking work (assuming the PEP is still accepted today as planned - just getting things in place before I go away for the weekend).

• Mark existing installer as deprecated in installer
• Mark existing installer as deprecated in docs
• Add --preset-pymanager support to PC/layout script
• Add deprecation warning to legacy py.exe when used with commands
• Update using/windows docs

Linked PRs

• gh-132930: Implement PEP 773 #132931
• gh-132930: Improve names of IDLE and PyDoc shortcuts #133091
• GH-132930: Display 'free-threaded' in pymanager builds #133119
• GH-132930: Fix use of ALIAS_WPREFIX in pymanager builds #133120
• gh-132930: Fixes PEP 514 registration for PyManager packages on x64 #133154
• gh-132930: Include IDLE path in registry for PyManager packages #133246