Backend plugins: Refactor to allow shared contract between core and external backend plugins (#25472)

Refactor to allow shared contract between core and external backend plugins 
allowing core backend data sources in Grafana to be implemented in same 
way as an external backend plugin.
Use v0.67.0 of sdk.
Add tests for verifying plugin is restarted when process is killed.
Enable strict linting for backendplugin packages

pkg/setting/setting.go

@@ -228,6 +228,16 @@ type Cfg struct {
 	AppSubUrl        string
 	ServeFromSubPath bool
 
+	// build
+	BuildVersion string
+	BuildCommit  string
+	BuildBranch  string
+	BuildStamp   int64
+	IsEnterprise bool
+
+	// packaging
+	Packaging string
+
 	// Paths
 	ProvisioningPath   string
 	DataPath           string
@@ -607,6 +617,13 @@ func (cfg *Cfg) Load(args *CommandLineArgs) error {
 	// Temporary keep global, to make refactor in steps
 	Raw = cfg.Raw
 
+	cfg.BuildVersion = BuildVersion
+	cfg.BuildCommit = BuildCommit
+	cfg.BuildStamp = BuildStamp
+	cfg.BuildBranch = BuildBranch
+	cfg.IsEnterprise = IsEnterprise
+	cfg.Packaging = Packaging
+
 	ApplicationName = APP_NAME
 
 	Env, err = valueAsString(iniFile.Section(""), "app_mode", "development")