Rename `util/profiler` package to `httputil` and refactor it:
* simplify utility HTTP server;
* make more generic server's parameters in order to remove `viper.Viper`
dependency;
* use single constructor for creating the pprof and prometheus servers;
* replace `enabled` config value with empty-check of the network address.
Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>
