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>

modules/web/routing/context.go

@@ -6,6 +6,9 @@ package routing
 import (
 	"context"
 	"net/http"
+
+	"code.gitea.io/gitea/modules/gtprof"
+	"code.gitea.io/gitea/modules/reqctx"
 )
 
 type contextKeyType struct{}
@@ -14,10 +17,12 @@ var contextKey contextKeyType
 
 // RecordFuncInfo records a func info into context
 func RecordFuncInfo(ctx context.Context, funcInfo *FuncInfo) (end func()) {
-	// TODO: reqCtx := reqctx.FromContext(ctx), add trace support
 	end = func() {}
-
-	// save the func info into the context record
+	if reqCtx := reqctx.FromContext(ctx); reqCtx != nil {
+		var traceSpan *gtprof.TraceSpan
+		traceSpan, end = gtprof.GetTracer().StartInContext(reqCtx, "http.func")
+		traceSpan.SetAttributeString("func", funcInfo.shortName)
+	}
 	if record, ok := ctx.Value(contextKey).(*requestRecord); ok {
 		record.lock.Lock()
 		record.funcInfo = funcInfo