Add link to CLI overview from install articles

[adegeo]

Summary

• Add next steps link to the CLI overview article.
• Where there were specific install instructions, follow up with a link to the CLI overview article.
• Changed the CLI overview article to have a better intro instead of a link farm right up top.

Fixes #40818
Fixes #40209

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Internal previews

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📄 File	🔗 Preview link
docs/core/install/linux-alpine.md	Install the .NET SDK or the .NET Runtime on Alpine
docs/core/install/linux-centos.md	Install .NET on CentOS Linux
docs/core/install/linux-debian.md	Install the .NET SDK or the .NET Runtime on Debian
docs/core/install/linux-fedora.md	docs/core/install/linux-fedora
docs/core/install/linux-opensuse.md	Install the .NET SDK or the .NET Runtime on openSUSE
docs/core/install/linux-rhel.md	Install .NET on RHEL and CentOS Stream
docs/core/install/linux-scripted-manual.md	Install .NET on Linux by using an install script or by extracting binaries
docs/core/install/linux-sles.md	docs/core/install/linux-sles
docs/core/install/linux-snap-runtime.md	Install .NET Runtime with Snap
docs/core/install/linux-snap-sdk.md	Install .NET SDK on Linux with Snap
docs/core/install/linux-ubuntu-install.md	Install .NET SDK or .NET Runtime on Ubuntu
docs/core/install/linux-ubuntu.md	Get OS version info
docs/core/install/macos.md	docs/core/install/macos
docs/core/install/upgrade.md	Upgrade to a new .NET version
docs/core/install/windows.md	Install .NET on Windows
docs/core/tools/index.md	.NET CLI

[tdykstra]

This is definitely an improvement to the article structure! I left a few suggestions that I think may help newcomers to the CLI.