hreflang tag values should be derived from the canonical URL, not the request URL

[jonoaldersonwp]

Many of our pages use hreflang tags to indicate localised/translated variants. That value that they output is currently based on the request URL.

E.g., https://wordpress.org/download/?test=1234 outputs alternate URLs like https://bs.wordpress.org/download/?test=1234.

This is incorrect; the alternate values should be derived fom the requested page's canonical URL.

E.g., https://wordpress.org/download/?test=1234 should output alternate URLs like https://bs.wordpress.org/download/.

[dd32]

In 7898:

WordPress.org: hreflang: Add a default x-default hreflang tag and use the canonical URL for singular pages when possible.

Fixes #3947, #3948.