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/feed/render.go

@@ -9,7 +9,7 @@ import (
 
 // RenderBranchFeed render format for branch or file
 func RenderBranchFeed(ctx *context.Context) {
-	_, _, showFeedType := GetFeedType(ctx.PathParam(":reponame"), ctx.Req)
+	_, _, showFeedType := GetFeedType(ctx.PathParam("reponame"), ctx.Req)
 	if ctx.Repo.TreePath == "" {
 		ShowBranchFeed(ctx, ctx.Repo.Repository, showFeedType)
 	} else {