chore(all): return concrete types, accept interfaces

- Remove exported interfaces unused locally
- Define interfaces to accept arguments
- Return concrete types, not interfaces

internal/httpproxy/settings.go

@@ -4,11 +4,8 @@ import (
 	"context"
 
 	"github.com/qdm12/gluetun/internal/configuration/settings"
-	"github.com/qdm12/gluetun/internal/httpproxy/state"
 )
 
-type SettingsGetSetter = state.SettingsGetSetter
-
 func (l *Loop) GetSettings() (settings settings.HTTPProxy) {
 	return l.state.GetSettings()
 }