Firmware download/upgrade/prerequisites cleanup

[tlaurion]

WiP.

As of now changes are visible from these pages:

• https://tlaurion.github.io/heads-wiki/ (added another Step 1 - Downloading)
• https://tlaurion.github.io/heads-wiki/Downloading
• https://tlaurion.github.io/heads-wiki/Updating
• https://tlaurion.github.io/heads-wiki/Prerequisites
• https://tlaurion.github.io/heads-wiki/community/
• https://tlaurion.github.io/heads-wiki/Keys/#tpm-pcrs (to end of page)

Present goals of this PR:

• [x] Have a cleaner view of how to upgrade firmware addressing concerns of fearful users (including Legacy to Maximized builds)
• [x] Have a clearer view of how to download firmware from CI
• [x] Cross-link download/build instructions. Move things away
• [x] Have TOC where needed on top of modified pages
• [x] Remove duplicates from Flashing instructions, Generic build instructions and cross-link where needed instead.
• [ ] Move snippets/simplify docs that are at https://zerolink.ml/1DMb3CV66qZPwJqkgm4z12nu8BrAwDoD4g/?Post:57 following feedback from community

[tlaurion]

Tagging past heads-wiki top contributors for review: @Thrilleratplay @jtmoree-github-com

@merge: makes sense? (specifically https://tlaurion.github.io/heads-wiki/Downloading/#what-to-downloadhow-to-upgrade)

@MrChromebox : for approval (this is an important change)

[MrChromebox]

Boot your Heads laptop, go into Recovery Shell to make sure if you should download Legacy or Maximized board ROMs:

this is applicable only for a subset of boards supported by Heads, and needs to be prefaced as such, given it's the first item on the Download page

[tlaurion]

Boot your Heads laptop, go into Recovery Shell to make sure if you should download Legacy or Maximized board ROMs:

this is applicable only for a subset of boards supported by Heads, and needs to be prefaced as such, given it's the first item on the Download page

@MrChromebox : Linking to https://tlaurion.github.io/heads-wiki/Prerequisites#supported-devices here again? "If you own a board offering a Maximized version but are not yet under a Maximized board ...."

This is the loop I'm trying to address here :)

[MrChromebox]

@tlaurion probably, probably in the context of a sentence mentioning applicability

[tlaurion]

Next will be to update https://osresearch.net/heads-wiki/Configuring-Keys/ with fresh screenshots, remove Recovery shell totpseal.sh output, and move Owning states content from Updating to Configure-Keys

But that is gonna be another PR.