+ config: add "debug_pprof" setting

Squashed commit of the following:

commit 96d185cf4acc55b21a00d10072e0a641ef7655b8
Merge: 3b75a8cb 9b7c1181
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Apr 22 15:57:50 2020 +0300

    Merge remote-tracking branch 'origin/master' into add-pprof

commit 3b75a8cbec5d72be8865a56bfd7ebb8b0673c3bc
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Apr 22 13:52:36 2020 +0300

    * use localhost:6060 for pprof

commit f66f2fbd7409b98cd9f7d297c268fca998f85e3b
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Apr 22 12:46:25 2020 +0300

    minor

commit 6e38712fb5542f612675858eb957efdefc38f9b0
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Wed Apr 22 11:59:39 2020 +0300

    use separate HTTP server for pprof

commit 988d95b5fad22f536bf9204b6b96f3697cf9a589
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Tue Apr 21 17:04:04 2020 +0300

    minor

commit 90ee6e9753be2af49467687cdf71c35b3943b78b
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Tue Apr 21 16:57:38 2020 +0300

    * use modified version of pprof

commit 413002220fe0717950539a8b7e6b0f31cef31bb8
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Mon Apr 20 16:35:21 2020 +0300

    minor

commit d4655d3849de1d9fe97efdb7f18fc21d5ac19eda
Author: Simon Zolin <s.zolin@adguard.com>
Date:   Mon Apr 20 15:57:57 2020 +0300

    + config: add "enable_pprof" setting

.golangci.yml

@@ -13,6 +13,7 @@ run:
   skip-files:
     - ".*generated.*"
     - dnsfilter/rule_to_regexp.go
+    - util/pprof.go
     - ".*_test.go"
 
 
@@ -65,5 +66,7 @@ issues:
     - Error return value of ..*.Shutdown.
     # goconst
     - string .forcesafesearch.google.com. has 3 occurrences
+    # gosec: Profiling endpoint is automatically exposed on /debug/pprof
+    - G108
     # gosec: Subprocess launched with function call as argument or cmd arguments
-    - G204
+    - G204