Support new network-related markers to break up the phase "waiting for socket thread" in network markers

[julienw]

see https://bugzilla.mozilla.org/show_bug.cgi?id=1618687 for more context

┆Issue is synchronized with this Jira Task

[acreskeyMoz]

This patch shows the three markers with an intProperty, "channelId" https://phabricator.services.mozilla.com/D220614

(now being given the MarkerThreadId::MainThread() marker option on @julienw 's suggestion)