feat: deprecate observer output (#367)

* feat: deprecate observer output

* Update core.go

Author: kruskall

logp/core.go

@@ -417,6 +417,8 @@ func TestingSetup(options ...Option) error {
 
 // ObserverLogs provides the list of logs generated during the observation
 // process.
+//
+// Deprecated: Use logptest.NewTestingLoggerWithObserver.
 func ObserverLogs() *observer.ObservedLogs {
 	return loadLogger().observedLogs
 }

logp/options.go

@@ -37,6 +37,8 @@ func WithSelectors(selectors ...string) Option {
 
 // ToObserverOutput specifies that the output should be collected in memory so
 // that they can be read by an observer by calling ObserverLogs().
+//
+// Deprecated: Use logptest.NewTestingLoggerWithObserver.
 func ToObserverOutput() Option {
 	return func(cfg *Config) {
 		cfg.toObserver = true