go/analysis/passes/unusedresult: add functions from slices package

This change adds to the list various slice-altering functions
whose result it is a mistake to ignore.

Change-Id: I0ecdd55b19760c44120e91b198a7f74b1c460bdc
Reviewed-on: https://go-review.googlesource.com/c/tools/+/554317
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

go/analysis/passes/unusedresult/unusedresult.go

@@ -59,7 +59,25 @@ func init() {
 	// List standard library functions here.
 	// The context.With{Cancel,Deadline,Timeout} entries are
 	// effectively redundant wrt the lostcancel analyzer.
-	funcs.Set("errors.New,fmt.Errorf,fmt.Sprintf,fmt.Sprint,sort.Reverse,context.WithValue,context.WithCancel,context.WithDeadline,context.WithTimeout")
+	funcs = stringSetFlag{
+		"context.WithCancel":   true,
+		"context.WithDeadline": true,
+		"context.WithTimeout":  true,
+		"context.WithValue":    true,
+		"errors.New":           true,
+		"fmt.Errorf":           true,
+		"fmt.Sprint":           true,
+		"fmt.Sprintf":          true,
+		"slices.Clip":          true,
+		"slices.Compact":       true,
+		"slices.CompactFunc":   true,
+		"slices.Delete":        true,
+		"slices.DeleteFunc":    true,
+		"slices.Grow":          true,
+		"slices.Insert":        true,
+		"slices.Replace":       true,
+		"sort.Reverse":         true,
+	}
 	Analyzer.Flags.Var(&funcs, "funcs",
 		"comma-separated list of functions whose results must be used")