Improve clarity and CTA of Install section

[jessicaschilling]

The existing https://ipfs.io/#install section has issues:

• Lacking clarity of messaging for who should install what in order to meet which needs
• Too many CTAs in one place, leading to conflicting messaging
• No metrics captured on user actions

Rework this section in order to start collecting actionable metrics and provide a starting point for future improvements. This isn't strictly necessary at time of site relaunch, but would be a good value-add for both users and the core team.

Preliminary work was researched and tested in https://ipfs-ia-scratchpad.netlify.app/#install, but this will need to be tweaked and potentially re-tested for renewed PMF focus.

Note that there's been discussion about an improved download section potentially replacing https://js.ipfs.io to reduce maintainership burden — if so, need to make sure a reasonable degree of content parity exists, as well as add the relevant deprecation/redirection issues in that site's repo.