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/api/v1/user/follower.go

@@ -201,7 +201,7 @@ func CheckFollowing(ctx *context.APIContext) {
 	//   "404":
 	//     "$ref": "#/responses/notFound"
 
-	target := GetUserByParamsName(ctx, ":target")
+	target := GetUserByPathParam(ctx, "target") // FIXME: it is not right to call this function, it should load the "target" directly
 	if ctx.Written() {
 		return
 	}