net/http: add Protocols field to Server and Transport
Support configuring which HTTP version(s) a server or client use
via an explicit set of protocols. The Protocols field takes
precedence over TLSNextProto and ForceAttemptHTTP2.
Fixes #67814
Change-Id: I09ece88f78ad4d98ca1f213157b5f62ae11e063f
Reviewed-on: https://go-review.googlesource.com/c/go/+/607496
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Jonathan Amsterdam <jba@google.com> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>