fix: Implement CheckerDefinitionProvider on tlsProvider

Lets the SDK seed OptionEndpoints from the primary's DiscoverEntries
output when checker-tls runs as a sibling.

plugin/plugin.go

@@ -9,5 +9,6 @@ var Version = "custom-build"
 
 func NewCheckerPlugin() (*sdk.CheckerDefinition, sdk.ObservationProvider, error) {
 	tls.Version = Version
-	return tls.Definition(), tls.Provider(), nil
+	prvd := tls.Provider()
+	return prvd.(sdk.CheckerDefinitionProvider).Definition(), prvd, nil
 }