[chore] Upgrade koanf to v2 in the Supervisor (open-telemetry#25169)

This is primarily to align the version with what the Collector uses in
`confmap`. It doesn't introduce any functional changes.

cmd/opampsupervisor/go.mod

@@ -4,7 +4,10 @@ go 1.19
 
 require (
 	github.com/cenkalti/backoff/v4 v4.2.0
-	github.com/knadh/koanf v1.5.0
+	github.com/knadh/koanf/parsers/yaml v0.1.0
+	github.com/knadh/koanf/providers/file v0.1.0
+	github.com/knadh/koanf/providers/rawbytes v0.1.0
+	github.com/knadh/koanf/v2 v2.0.1
 	github.com/oklog/ulid/v2 v2.1.0
 	github.com/open-telemetry/opamp-go v0.6.0
 	go.opentelemetry.io/collector/config/configtls v0.82.0
@@ -15,6 +18,7 @@ require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/fsnotify/fsnotify v1.6.0 // indirect
 	github.com/gorilla/websocket v1.5.0 // indirect
+	github.com/knadh/koanf/maps v0.1.1 // indirect
 	github.com/mitchellh/copystructure v1.2.0 // indirect
 	github.com/mitchellh/mapstructure v1.5.0 // indirect
 	github.com/mitchellh/reflectwalk v1.0.2 // indirect