Bug 1563680 - Move network monitor actor files into the network-monitor directory r=Honza

Moved network monitor actor files:

network-monitor.js
network-event.js

into devtools/server/actors/network-monitor directory.

And updated moz.build files presented in related directories.

Differential Revision: https://phabricator.services.mozilla.com/D38219

--HG--
rename : devtools/server/actors/network-event.js => devtools/server/actors/network-monitor/network-event.js
rename : devtools/server/actors/network-monitor.js => devtools/server/actors/network-monitor/network-monitor.js
extra : moz-landing-system : lando

devtools/server/actors/moz.build

@@ -39,8 +39,6 @@ DevToolsModules(
     'highlighters.js',
     'layout.js',
     'memory.js',
-    'network-event.js',
-    'network-monitor.js',
     'object.js',
     'pause-scoped.js',
     'perf.js',

devtools/server/actors/network-monitor/moz.build

@@ -6,6 +6,8 @@
 
 DevToolsModules(
     'channel-event-sink.js',
+    'network-event.js',
+    'network-monitor.js',
     'network-observer.js',
     'network-response-listener.js',
     'stack-trace-collector.js',