x/pkgsite: Sub-repositories list is incomplete

[treuherz]

What is the URL of the page with the issue?

https://pkg.go.dev/golang.org/x

Screenshot

What did you expect to see?

All the x subrepos in the go codebase, as listed on https://cs.opensource.google/go

What did you see instead?

Only some of them, missing useful packages like oauth2 and term and making them less discoverable.

It seems like there might have been some deliberate filtering here, to leave out outdated packages like xerrors and vgo, but it's not clear whether all the omissions are on purpose. If we want them added then I'd be happy to raise a PR for it, but I wanted to check in case there was a rationale I was missing.

[seankhliao]

Duplicate of #37265