Fix merge conflict and apply SME feedback

[bobfuru]

This PR incorporates feedback from CoreOS SMEs, compiled from separate PRs:

• Replaces install: ignition_url/rootfs_url only supports HTTP and HTTPS #25989 due to a merge conflict. Addresses @miabbott's changes and @bgilbert's note about coreos.live.rootfs_url.
• Addresses the comments from @bgilbert in OSDOCS-1496 - Advanced networking tables #25656. Ben: I have responded to your edits in that PR, but it was already merged, so it might make more sense to just review this fresh PR for a sanity check. Much appreciated!

This work also relates to #25709. It's likely that 25709 will be merged first, hopefully without resulting merge conflicts. 🤞

[openshift-docs-preview-bot]

The preview will be available shortly at:

• https://COREOS-updates--ocpdocs.netlify.com/

[bobfuru]

@miabbott and @bgilbert PTAL and let me know if you have changes, or if this looks good to you, thanks!

[miabbott]

LGTM! I don't think I saw anything to prevent merging; fixes can be done in a follow-up

[bobfuru]

/cherrypick enterprise-4.6

[openshift-cherrypick-robot]

@bobfuru: #26070 failed to apply on top of branch "enterprise-4.6":

Applying: Fix merge conflict and apply SME feedback
Using index info to reconstruct a base tree...
M	modules/installation-user-infra-machines-iso.adoc
Falling back to patching base and 3-way merge...
Auto-merging modules/installation-user-infra-machines-iso.adoc
CONFLICT (content): Merge conflict in modules/installation-user-infra-machines-iso.adoc
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Fix merge conflict and apply SME feedback
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

Details

In response to this:

/cherrypick enterprise-4.6

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[bobfuru]

Fix for 4.6 CP merge conflict in #26093

[bobfuru]

Thanks, @bgilbert - I have addressed your most recent comments in #26442 to combine with your additional feedback. Please double-check in either PR and let me know if these changes are as you intended or not.