gopls/internal/server: add counters for add and remove struct tags

One telemetry counter for add struct tags codeaction and one
for remove struct tags codeaction.

For golang/go#74568
Change-Id: I5c45167f87eea5639a16ee2fc0275adc0ff03ad4
Reviewed-on: https://go-review.googlesource.com/c/tools/+/688156
Reviewed-by: Robert Findley <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: madelinekalil

gopls/internal/server/command.go

@@ -1806,8 +1806,13 @@ func (c *commandHandler) ModifyTags(ctx context.Context, args command.ModifyTags
 		}
 		m.Transform = transform
 
+		// Each command involves either adding or removing tags, depending on
+		// whether Add or Clear is set.
 		if args.Add != "" {
+			countAddStructTags.Inc()
 			m.Add = strings.Split(args.Add, ",")
+		} else if args.Clear {
+			countRemoveStructTags.Inc()
 		}
 		if args.AddOptions != "" {
 			if options, err := optionsStringToMap(args.AddOptions); err != nil {

gopls/internal/server/counters.go

@@ -35,3 +35,11 @@ var (
 
 	countRename = counter.New("gopls/rename")
 )
+
+// Proposed counters for evaluating gopls refactoring codeactions add struct
+// tags and remove struct tags.
+var (
+	countAddStructTags = counter.New("gopls/structtags:add")
+
+	countRemoveStructTags = counter.New("gopls/structtags:remove")
+)