[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/config.go

@@ -0,0 +1,57 @@
+package plugins
+
+import (
+	"github.com/grafana/grafana/pkg/setting"
+)
+
+type Cfg struct {
+	DevMode bool
+
+	PluginsPath string
+
+	PluginSettings       setting.PluginSettings
+	PluginsAllowUnsigned []string
+
+	EnterpriseLicensePath string
+
+	// AWS Plugin Auth
+	AWSAllowedAuthProviders []string
+	AWSAssumeRoleEnabled    bool
+
+	// Azure Cloud settings
+	Azure setting.AzureSettings
+
+	CheckForUpdates bool
+
+	BuildVersion string // TODO Remove
+	AppSubURL    string // TODO Remove
+}
+
+func NewCfg() *Cfg {
+	return &Cfg{}
+}
+
+func FromGrafanaCfg(grafanaCfg *setting.Cfg) *Cfg {
+	cfg := &Cfg{}
+
+	cfg.DevMode = grafanaCfg.Env == setting.Dev
+	cfg.PluginsPath = grafanaCfg.PluginsPath
+
+	cfg.PluginSettings = grafanaCfg.PluginSettings
+	cfg.PluginsAllowUnsigned = grafanaCfg.PluginsAllowUnsigned
+	cfg.EnterpriseLicensePath = grafanaCfg.EnterpriseLicensePath
+
+	// AWS
+	cfg.AWSAllowedAuthProviders = grafanaCfg.AWSAllowedAuthProviders
+	cfg.AWSAssumeRoleEnabled = grafanaCfg.AWSAssumeRoleEnabled
+
+	// Azure
+	cfg.Azure = grafanaCfg.Azure
+
+	cfg.CheckForUpdates = grafanaCfg.CheckForUpdates
+
+	cfg.BuildVersion = grafanaCfg.BuildVersion
+	cfg.AppSubURL = grafanaCfg.AppSubURL
+
+	return cfg
+}