x/pkgsite: search for math/rand should answer with math/rand/v2 too

[pjweinb]

What is the URL of the page with the issue?

https://pkg.go.dev/math/rand

What is your user agent?

irrelevant

Screenshot

No response

What did you do?

i searched for math/rand

What did you see happen?

it gave me math/rand

What did you expect to see?

i expected to see some mention of the new replacement package math/rand/v2

[jfrech]

Since /vn is an encouraged practice, the pkgsite may benefit from a generic "new package versions exist" notice.

[seankhliao]

Duplicate of #68711