pdata: add [Type]Slice.Sort(func) to sort slices (#3671)

* pdata: add TypeSlice.Sort(func) to sort slices

Comparing two generated slices can be tedious when the slices are not
ordered, and order does not matter for the test.

This change adds a .Sort(func(i, j int) bool) method to generated [Type]Slice. This is
similar to method StringMap.Sort(), but takes a less function because
the order may differ by context, where the sort order of a map is obvious (by key).

* fix: improve TypeSlice.Sort(less) signature

* fix: resolve goimports CI check

* chore: make genpdata

cmd/pdatagen/internal/base_slices.go

@@ -200,7 +200,22 @@ func (es ${structName}) EnsureCapacity(newCap int) {
 func (es ${structName}) AppendEmpty() ${elementName} {
 	*es.orig = append(*es.orig, &${originName}{})
 	return es.At(es.Len() - 1)
-} `
+}
+
+// Sort sorts the ${elementName} elements within ${structName} given the
+// provided less function so that two instances of ${structName}
+// can be compared.
+//
+// Returns the same instance to allow nicer code like:
+//   lessFunc := func(a, b ${elementName}) bool {
+//     return a.Name() < b.Name() // choose any comparison here
+//   }
+//   assert.EqualValues(t, expected.Sort(lessFunc), actual.Sort(lessFunc))
+func (es ${structName}) Sort(less func(a, b ${elementName}) bool) ${structName} {
+	sort.SliceStable(*es.orig, func(i, j int) bool { return less(es.At(i), es.At(j)) })
+	return es
+}
+`
 
 const slicePtrTestTemplate = `func Test${structName}(t *testing.T) {
 	es := New${structName}()

cmd/pdatagen/internal/log_structs.go

@@ -17,6 +17,8 @@ package internal
 var logFile = &File{
 	Name: "log",
 	imports: []string{
+		`"sort"`,
+		``,
 		`otlplogs "go.opentelemetry.io/collector/model/internal/data/protogen/logs/v1"`,
 	},
 	testImports: []string{

cmd/pdatagen/internal/metrics_structs.go

@@ -17,6 +17,8 @@ package internal
 var metricsFile = &File{
 	Name: "metrics",
 	imports: []string{
+		`"sort"`,
+		``,
 		`otlpmetrics "go.opentelemetry.io/collector/model/internal/data/protogen/metrics/v1"`,
 	},
 	testImports: []string{

cmd/pdatagen/internal/trace_structs.go

@@ -17,6 +17,8 @@ package internal
 var traceFile = &File{
 	Name: "trace",
 	imports: []string{
+		`"sort"`,
+		``,
 		`otlptrace "go.opentelemetry.io/collector/model/internal/data/protogen/trace/v1"`,
 	},
 	testImports: []string{