Bug 1421651 - Remove obseleted timeline and TimelineMarker code r=canaltinova,webidl,devtools-reviewers,saschanaz,smaug,ochameau

This patch removes the old docshell timeline and timeline markers codebase and replaces them with equivalent Gecko profiler marker. This patch also fixes Bug 1834143, which is a subset of 1421651.

Differential Revision: https://phabricator.services.mozilla.com/D184217

Author: AdamBrouwersHarries

devtools/client/netmonitor/test/browser.toml

@@ -388,8 +388,6 @@ skip-if = ["os == 'win'"] # bug 1391264
 
 ["browser_net_reload-button.js"]
 
-["browser_net_reload-markers.js"]
-
 ["browser_net_req-resp-bodies.js"]
 
 ["browser_net_resend.js"]