[WIP] Plugins: Refactoring backend initialization flow (#42247)

* refactoring store interface and init flow

* fix import

* fix linter

* refactor resource calling

* load with class

* re-order args

* fix tests

* fix linter

* remove old creator

* add custom config struct

* fix some tests

* cleanup

* fix linter

* add connect failure error

* remove unused err

* convert test over

pkg/plugins/manager/manager_integration_test.go

@@ -7,6 +7,7 @@ import (
 	"testing"
 
 	"github.com/grafana/grafana/pkg/plugins"
+	"github.com/grafana/grafana/pkg/plugins/backendplugin/provider"
 	"github.com/grafana/grafana/pkg/plugins/manager/loader"
 	"github.com/grafana/grafana/pkg/plugins/manager/signature"
 	"github.com/grafana/grafana/pkg/services/licensing"
@@ -42,9 +43,10 @@ func TestPluginManager_int_init(t *testing.T) {
 	license := &licensing.OSSLicensingService{
 		Cfg: cfg,
 	}
-	pm := newManager(cfg, nil, loader.New(license, cfg, &signature.UnsignedPluginAuthorizer{Cfg: cfg}), nil)
 
-	err = pm.init()
+	pmCfg := plugins.FromGrafanaCfg(cfg)
+	pm, err := ProvideService(cfg, nil, loader.New(pmCfg, license,
+		&signature.UnsignedPluginAuthorizer{Cfg: pmCfg}, &provider.Service{}), nil)
 	require.NoError(t, err)
 
 	verifyCorePluginCatalogue(t, pm)