Move the cloud output to the new Output interface

[na--]

Follow up to #1869 and #1870. Closes #1258 and moves the cloud output to the new Output interface.

[mstoykov]

LGTM.

[mstoykov]

actually just checked 2 or 3 things I wasn't sure about with the config and a thing that definitely doesn't work is picking up my subscription from the config file

[codecov-io]

Codecov Report

Merging #1874 (2ef51b5) into master (a44f5dc) will increase coverage by 0.13%.
The diff coverage is 58.82%.

@@            Coverage Diff             @@
##           master    #1874      +/-   ##
==========================================
+ Coverage   71.03%   71.16%   +0.13%     
==========================================
  Files         183      183              
  Lines       14316    14306      -10     
==========================================
+ Hits        10169    10181      +12     
+ Misses       3530     3497      -33     
- Partials      617      628      +11     

Flag	Coverage Δ
ubuntu	71.10% <58.82%> (+0.09%)	⬆️
windows	70.78% <58.82%> (+0.20%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
cloudapi/util.go	0.00% <0.00%> (ø)
cmd/outputs.go	0.00% <0.00%> (ø)
output/cloud/cloud_easyjson.go	33.33% <ø> (ø)
output/cloud/data.go	90.97% <ø> (ø)
stats/csv/collector.go	83.83% <ø> (+0.67%)	⬆️
stats/influxdb/collector.go	81.30% <ø> (+1.49%)	⬆️
stats/kafka/collector.go	53.33% <ø> (+1.72%)	⬆️
stats/statsd/common/collector.go	82.71% <ø> (+0.78%)	⬆️
output/cloud/output.go	78.66% <64.93%> (ø)
js/runner.go	80.86% <0.00%> (-0.58%)	⬇️
... and 1 more

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[na--]

This is now ready for merging from my side, I've renamed all Collector / c mentions to Output / out, and I've cleaned up some of the linter issues that were present. I suggest reading the changes commit by commit.