fix: unify koanf delimiter to otel (#33214)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->

**Link to tracking Issue:**
Fixes #31925

Signed-off-by: odubajDT <ondrej.dubaj@dynatrace.com>

cmd/opampsupervisor/supervisor/supervisor.go

@@ -718,7 +718,7 @@ func (s *Supervisor) setupOwnMetrics(_ context.Context, settings *protobufs.Tele
 // 3) the local override config that is hard-coded in the Supervisor.
 func (s *Supervisor) composeEffectiveConfig(config *protobufs.AgentRemoteConfig) (configChanged bool, err error) {
 
-	var k = koanf.New(".")
+	var k = koanf.New("::")
 
 	// Begin with empty config. We will merge received configs on top of it.
 	if err = k.Load(rawbytes.Provider([]byte{}), yaml.Parser()); err != nil {
@@ -747,7 +747,7 @@ func (s *Supervisor) composeEffectiveConfig(config *protobufs.AgentRemoteConfig)
 			if item == nil {
 				continue
 			}
-			var k2 = koanf.New(".")
+			var k2 = koanf.New("::")
 			err = k2.Load(rawbytes.Provider(item.Body), yaml.Parser())
 			if err != nil {
 				return false, fmt.Errorf("cannot parse config named %s: %w", name, err)