Add +Inf bucket and Refactor out append_labels function.
+Inf bucket is essentially a copy of _count
its required to properly calculate histogram_quantile
query function.
Initially I wanted to implemnt the copy of _count in C thus small refactoring. However its not a lot of overhead to add another "submetric" that will store the value of +Inf.
Edited by Paweł Chojnacki