[Sets] Add Read lock to new Union and ShallowCopy (#564)

* add read locks to shallow copy and unionSortedSet

* add changelog

changelog/v0.40.1/sets-union-addRlock.yaml

@@ -0,0 +1,5 @@
+changelog:
+  - type: NON_USER_FACING
+    description: >
+      "Adds Read Lock to ShallowCopy and Union methods on sets"
+    skipCI: "false"

contrib/pkg/sets/v2/sets.go

@@ -246,6 +246,8 @@ func (s *resourceSet[T]) Union(set ResourceSet[T]) ResourceSet[T] {
 // Assuming that the argument set is sorted by resource id,
 // this method will efficiently union the two sets together and return the unioned set.
 func (s *resourceSet[T]) unionSortedSet(set ResourceSet[T]) *resourceSet[T] {
+	s.lock.RLock()
+	defer s.lock.RUnlock()
 	merged := make([]T, 0, len(s.set)+set.Len())
 	idx := 0
 
@@ -373,6 +375,8 @@ func (oldSet *resourceSet[T]) Clone() ResourceSet[T] {
 }
 
 func (oldSet *resourceSet[T]) ShallowCopy() ResourceSet[T] {
+	oldSet.lock.RLock()
+	defer oldSet.lock.RUnlock()
 	newSet := make([]T, len(oldSet.set))
 	copy(newSet, oldSet.set)
 	return &resourceSet[T]{