Support performance trace (#32973)

1. Add a OpenTelemetry-like shim-layer to collect traces
2. Add a simple builtin trace collector and exporter, end users could
download the diagnosis report to get the traces.

This PR's design is quite lightweight, no hard-dependency, and it is
easy to improve or remove. We can try it on gitea.com first to see
whether it works well, and fine tune the details.

---------

Co-authored-by: silverwind <me@silverwind.io>

cmd/web.go

@@ -18,10 +18,12 @@ import (
 
 	"code.gitea.io/gitea/modules/container"
 	"code.gitea.io/gitea/modules/graceful"
+	"code.gitea.io/gitea/modules/gtprof"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/process"
 	"code.gitea.io/gitea/modules/public"
 	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
 	"code.gitea.io/gitea/routers"
 	"code.gitea.io/gitea/routers/install"
 
@@ -218,6 +220,8 @@ func serveInstalled(ctx *cli.Context) error {
 		}
 	}
 
+	gtprof.EnableBuiltinTracer(util.Iif(setting.IsProd, 2000*time.Millisecond, 100*time.Millisecond))
+
 	// Set up Chi routes
 	webRoutes := routers.NormalRoutes()
 	err := listen(webRoutes, true)