embed.FS is the implementation of embedded file trees, providing
an fs.FS for each embed.FS variable.
Tests are in a follow-up CL, in the package embed/internal/embedtest.
(They can only be written once the toolchain can initialize one of these,
which requires changes to cmd/compile and cmd/go.)
For #41191.
Change-Id: Ieb0ead1d305cdac3d5d4e11772dca75740a72730
Reviewed-on: https://go-review.googlesource.com/c/go/+/243942
Trust: Russ Cox <rsc@golang.org>
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Rob Pike <r@golang.org> Reviewed-by: Jay Conrod <jayconrod@google.com>