feat(coderd): add times_used to coder_apps in insights API (#13292)

For now, only applied to `coder_app`s, same logic can be implemented for
VS Code, SSH, etc.

Part of #13099

codersdk/insights.go

@@ -217,6 +217,7 @@ type TemplateAppUsage struct {
 	Slug        string           `json:"slug" example:"vscode"`
 	Icon        string           `json:"icon"`
 	Seconds     int64            `json:"seconds" example:"80500"`
+	TimesUsed   int64            `json:"times_used" example:"2"`
 }
 
 // TemplateParameterUsage shows the usage of a parameter for one or more