Clarify path param naming (#32969)

In history (from some legacy frameworks), both `:name` and `name` are
supported as path path name, `:name` is an alias to `name`.

To make code consistent, now we should only use `name` but not `:name`.

Also added panic check in related functions to make sure the name won't
be abused in case some downstreams still use them.

routers/web/org/home.go

@@ -28,14 +28,14 @@ const (
 
 // Home show organization home page
 func Home(ctx *context.Context) {
-	uname := ctx.PathParam(":username")
+	uname := ctx.PathParam("username")
 
 	if strings.HasSuffix(uname, ".keys") || strings.HasSuffix(uname, ".gpg") {
 		ctx.NotFound("", nil)
 		return
 	}
 
-	ctx.SetPathParam(":org", uname)
+	ctx.SetPathParam("org", uname)
 	context.HandleOrgAssignment(ctx)
 	if ctx.Written() {
 		return