cmd: add a new analyzer for check missing values after append

cmd: add a new analyzer for check missing values after append

If there is no second parameter added during append, there will be no prompt when executing go vet. Add an analyzer to detect this situation

Update #60448

Change-Id: If9848835424f310c54e3e9377aaaad4a1516871a
Reviewed-on: https://go-review.googlesource.com/c/go/+/498416
Run-TryBot: shuang cui <imcusg@gmail.com>
Run-TryBot: Tim King <taking@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Tim King <taking@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>