tools.vpm: cleanup install part1

[ttytm]

Part1 of cleaning up the install procedure and making it more robust.

This PR changes consist of abstracting steps (used for both installations via a vpm shortcode and installations via a URL) into an install_module helper function. And simplifying by removing the need to use vpm_install and vpm_install_.

🤖 Generated by Copilot at 587f137

Refactored the vpm_install function in cmd/tools/vpm/vpm.v to improve code quality and support different module sources.

🤖 Generated by Copilot at 587f137

• Rename vpm_install_ function to vpm_install to avoid confusion (link, link)
• Split vpm_install function into vpm_install_from_vpm and vpm_install_from_vcs to make code more modular and readable (link, link)
• Add install_module function to encapsulate logic of installing a module from a given VCS, URL, and path (link)
• Replace calls to os.execute with calls to install_module in vpm_install_from_vpm and vpm_install_from_vcs to avoid code duplication and improve error handling (link, link)
• Modify vpm_install_from_vcs to take a Source enum instead of a string as the vcs_key argument and convert it to a string inside the function (link)
• Remove redundant or outdated comment line (link)
• Remove empty line for formatting (link)
• Update call to vpm_install with Source.vpm to vpm_install_from_vpm in cmd/tools/vpm.v (link)