install-world: rework installer

Installer now can:

• Keep up to 3 different Scap version wheels on deployment server
• Avoid downloading wheels already present on deployment server
• Install a particular Scap host (master or target) with a specific Scap version while leaving all other hosts untouched

Options --install-targets-only and --batch serve no purpose after the changes and were removed. As a bit of backround context, the --batch flag was originally intended to allow some automated process (for us usually Puppet) to call the Scap installer; in the end that never actually happened

Bug: T380772