all: make use of stringslite.{HasPrefix, HasSuffix}

all: make use of stringslite.{HasPrefix, HasSuffix}

Just a code cleanup.

Change-Id: Ie887ab2c71de11b4844c4e6fd4e5aca3265ac3aa
Reviewed-on: https://go-review.googlesource.com/c/go/+/583216
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>