Reduce allocations (census-instrumentation#1204)

When creating a copy of a slice/map we already know the size/capacity that the target slice/map needs to be.
By using make and providing the capacity argument we avoid allocation memory to grow the slice/map.

trace/lrumap.go

@@ -44,7 +44,7 @@ func (lm lruMap) len() int {
 }
 
 func (lm lruMap) keys() []interface{} {
-	keys := []interface{}{}
+	keys := make([]interface{}, len(lm.cacheKeys))
 	for k := range lm.cacheKeys {
 		keys = append(keys, k)
 	}

trace/trace.go

@@ -345,31 +345,31 @@ func (s *Span) SetStatus(status Status) {
 }
 
 func (s *Span) interfaceArrayToLinksArray() []Link {
-	linksArr := make([]Link, 0)
+	linksArr := make([]Link, 0, len(s.links.queue))
 	for _, value := range s.links.queue {
 		linksArr = append(linksArr, value.(Link))
 	}
 	return linksArr
 }
 
 func (s *Span) interfaceArrayToMessageEventArray() []MessageEvent {
-	messageEventArr := make([]MessageEvent, 0)
+	messageEventArr := make([]MessageEvent, 0, len(s.messageEvents.queue))
 	for _, value := range s.messageEvents.queue {
 		messageEventArr = append(messageEventArr, value.(MessageEvent))
 	}
 	return messageEventArr
 }
 
 func (s *Span) interfaceArrayToAnnotationArray() []Annotation {
-	annotationArr := make([]Annotation, 0)
+	annotationArr := make([]Annotation, 0, len(s.annotations.queue))
 	for _, value := range s.annotations.queue {
 		annotationArr = append(annotationArr, value.(Annotation))
 	}
 	return annotationArr
 }
 
 func (s *Span) lruAttributesToAttributeMap() map[string]interface{} {
-	attributes := make(map[string]interface{})
+	attributes := make(map[string]interface{}, s.lruAttributes.len())
 	for _, key := range s.lruAttributes.keys() {
 		value, ok := s.lruAttributes.get(key)
 		if ok {
@@ -420,7 +420,7 @@ func (s *Span) lazyPrintfInternal(attributes []Attribute, format string, a ...in
 	var m map[string]interface{}
 	s.mu.Lock()
 	if len(attributes) != 0 {
-		m = make(map[string]interface{})
+		m = make(map[string]interface{}, len(attributes))
 		copyAttributes(m, attributes)
 	}
 	s.annotations.add(Annotation{
@@ -436,7 +436,7 @@ func (s *Span) printStringInternal(attributes []Attribute, str string) {
 	var a map[string]interface{}
 	s.mu.Lock()
 	if len(attributes) != 0 {
-		a = make(map[string]interface{})
+		a = make(map[string]interface{}, len(attributes))
 		copyAttributes(a, attributes)
 	}
 	s.annotations.add(Annotation{