Add support for RPM based distros

[bandogora]

I did not realize ProxmoxVED was where this was supposed to go until hitting this PR template. The Contributing Guidelines link on the README did not lead me in the right direction...

Trying to rebase 16 commits has made a mess of things and it looks like there has been some work in this area already on VED, so I'll leave this as a draft for reference/suggestion.

I can attempt to rebase if anything here looks useful.

✍️ Description

Added compatibility to install, update, and clean RPM based distros without breaking changes (as far as manual testing went).

• Updated misc/install.func, misc/build.func, misc/install.func, and misc/core.func to handle templates based on RPM
• Updated tools/pve/clean-lxcs.sh, tools/pve/update-lxcs-cron.sh, and tools/pve/update-lxcs.sh to handle templates based on RPM
• Added scripts for base OS templates (centos, rockylinux, almalinux, fedora, and openeuler)
• Minor linting around changes

🔗 Related Issue

Fixes #

✅ Prerequisites (X in brackets)

• Self-review completed – Code follows project standards.
• Tested thoroughly – Changes work as expected.
• No security risks – No hardcoded secrets, unnecessary privilege escalations, or permission issues.

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🛠️ Type of Change (X in brackets)

• 🐞 Bug fix – Resolves an issue without breaking functionality.
• ✨ New feature – Adds new, non-breaking functionality.
• 💥 Breaking change – Alters existing functionality in a way that may require updates.
• 🆕 New script – A fully functional and tested script or script set.
• 🌍 Website update – Changes to website-related JSON files or metadata.
• 🔧 Refactoring / Code Cleanup – Improves readability or maintainability without changing functionality.
• 📝 Documentation update – Changes to README, AppName.md, CONTRIBUTING.md, or other docs.