all: go fix -fix=buildtag std cmd (except for bootstrap deps, vendor)

When these packages are released as part of Go 1.18,
Go 1.16 will no longer be supported, so we can remove
the +build tags in these files.

Ran go fix -fix=buildtag std cmd and then reverted the bootstrapDirs
as defined in cmd/dist/buildtool.go, which need to continue
to build with Go 1.4 for now.

Also reverted vendor and cmd/vendor, which will need
to be updated in their own repos first.

Manual changes in runtime/pprof/mprof_test.go to adjust line numbers.

For #41184.

Change-Id: Ic0f93f7091295b6abc76ed5cd6e6746e1280861e
Reviewed-on: https://go-review.googlesource.com/c/go/+/344955
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

Cherry-picked-from: golang/go@f229e70

Author: rsc

html/fuzz.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gofuzz
-// +build gofuzz
 
 package html