Adjust Linux landing and Ubuntu pages

[adegeo]

Summary

• Moved the supported-distributions section to the top.
• Moved the method/pros/cons table to the Decide how to install .NET section.
• Added some more instructions in the backports section.
• Optimize TOC with displayname: linux for the distros.
• Promoted Ubuntu Install over the Overview in the TOC.
• Moved linux-ubuntu.md to linux-ubuntu-decision.md and retitled it the decision guide.
• Created a redirect from linux-ubuntu.md to linux-ubuntu-install.md.
• Removed old redirects for the old ubuntu articles. Data indicates that 12 redirects were only used a total of 20 times within the last year.

Fixes #45126

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Internal previews

📄 File	🔗 Preview link
docs/core/install/index.yml	[linkListType: architecture
docs/core/install/linux-package-mixup.md	Troubleshoot .NET package mix ups on Linux
docs/core/install/linux-scripted-manual.md	Install .NET on Linux by using an install script or by extracting binaries
docs/core/install/linux-ubuntu-decision.md	Get OS version info which adds the $ID and $VERSION_ID variables
docs/core/install/linux-ubuntu-install.md	docs/core/install/linux-ubuntu-install
docs/core/install/linux.md	Install .NET on Linux
docs/fundamentals/toc.yml	docs/fundamentals/toc

[adegeo]

@BillWagner ready for review

[BillWagner]

This LGTM @adegeo

Let's