Fix shortname, update permanent redirects, improve xref

[tidoust]

This update sets the shortname of the spec to window-placement, updates URLs that return a permanent redirect (to save a redirect), and slightly improves references to external specs to better use xref mechanisms and get taken into account by Bikeshed when it builds its index and list of references.

Consideration sections would still need to be flagged as informative at some point so that external references they contain don't get listed as normative references but rather as informative references. Not done in this update because it triggers a bunch of "RFC2119 words in informative section" warnings.

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Preview | Diff

[anssiko]

Current status:

• [x] FPWD transition request approved https://github.com/w3c/transitions/issues/438
• [x] Awaiting publication to enter orbitRec Track. :rocket:

[tidoust]

Taking the liberty to merge. Suggested edits were made (and FPWD published some time ago)

[michaelwasserman]

Thanks for merging! The spec hasn't yet updated, but IIUC, the 'Build, Validate and Deploy' check should do that, right?

[inexorabletash]

Looks like that last run failed: https://github.com/w3c/window-placement/actions/runs/3060956376

[inexorabletash]

ah, this was likely due to the "HTML outage" where Bikeshed was temporarily borked. I've triggered a re-run

[inexorabletash]

Looks good now