net/http: add ServeFileFS, FileServerFS, NewFileTransportFS
These new apis are analogous to ServeFile, FileServer and NewFileTransport respectively. The main difference is that these functions operate on an fs.FS.
Fixes #51971
Change-Id: Ie56b245b795eeb7edf613657578592306945469b
GitHub-Last-Rev:
26e75c0368f155a2299fbdcb72f47036b71a5e06
GitHub-Pull-Request: golang/go#61641
Reviewed-on: https://go-review.googlesource.com/c/go/+/513956
Run-TryBot: Damien Neil <dneil@google.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>