net/http: bad handling of HEAD requests with a body [1.18 backport]

[dr2chase]

This is a by-hand backport request to 1.18 for #53960.
We approved the #56154 (1.19 backport today) and by default backports target the last two releases, so this backport is also approved.

[gopherbot]

Change https://go.dev/cl/457275 mentions this issue: [release-branch.go1.18] net/http: accept HEAD requests with a body

[gopherbot]

Change https://go.dev/cl/457416 mentions this issue: [internal-branch.go1.18-vendor] http2: accept HEAD requests with a body

[gopherbot]

Change https://go.dev/cl/457596 mentions this issue: [release-branch.go1.18] all: upgrade golang.org/x/net to v0.0.0-20221214163811-6143a133e5c9

[gopherbot]

Closed by merging d17cf56 to release-branch.go1.18.

[neild]

The backport for the HTTP/1 fix was never merged, thanks to none of us noticing that Gopherbot had prematurely closed this issue (#29599). Since there won't be another 1.18 minor release, this is unfortunate but there's not much to be done about that at this point.