Tags need to apply to events

[coccyx]

Tags set via env var are not applying to events currently, only to metrics. They should appear at the same level of the event as source.

[jrcheli]

I've tested this change with all event types: file, console, metric, http, net, fs, and dns.

As one example of this:
LD_PRELOAD=lib/linux/libscope.so SCOPE_TAG_hey=you SCOPE_EVENT_CONSOLE=true /bin/echo "something"
Outputs:
{"type":"evt","body":{"sourcetype":"console","id":"ubuntu18_4-echo-/bin/echo something","_time":1614357710.803,"source":"stdout","host":"ubuntu18_4","proc":"echo","cmd":"/bin/echo something","pid":110062,"_channel":"1414763257570779","hey":"you","data":"something"}}