Switch from `qm guest exec` to raw qemu-guest-agent socket interaction for provisioning commands

[KunoVonHagen]

Currently, provisioning commands on guest machines are executed using qm guest exec. Switching to direct, raw qemu-guest-agent socket interaction will improve provisioning command execution time and provide compatibility with guest operating systems not natively supported by Proxmox VE for qm guest exec.

Benefits:

• Faster execution of provisioning commands on guest machines
• Improved compatibility with a wider variety of guest OS (including those unsupported by Proxmox VE)
• Potential for greater control and extensibility when managing guest interactions

Proposed Tasks:

• Investigate current usage of qm guest exec in the codebase
• Implement raw socket communication for command execution via qemu-guest-agent
• Add configuration or abstraction layer for selecting execution method if needed
• Document the new approach and update relevant provisioning workflows

Acceptance Criteria:

• Provisioning commands are reliably and quickly executed via raw qemu-guest-agent socket interaction
• Backwards compatibility or clear migration guidance if qm guest exec is retained in any capacity
• Documentation is updated