Refactoring/aws/sns

[misg]

This PR aims to migrate AWS SNS service to the new architecture, as part of #183.
Please note that I removed subscriptions resources from the metadata.json file because they are already included in their topics resources (and displayed as so in the report, see above picture).

[codecov-io]

Codecov Report

Merging #265 into refactoring/resource-configs will increase coverage by 0.24%.
The diff coverage is 33.33%.

@@                       Coverage Diff                        @@
##           refactoring/resource-configs     #265      +/-   ##
================================================================
+ Coverage                         30.98%   31.23%   +0.24%     
================================================================
  Files                               130      141      +11     
  Lines                              5641     5869     +228     
================================================================
+ Hits                               1748     1833      +85     
- Misses                             3893     4036     +143

Impacted Files	Coverage Δ
...Suite/providers/aws/resources/sns/subscriptions.py	26.66% <26.66%> (ø)
ScoutSuite/providers/aws/resources/sns/topics.py	33.33% <33.33%> (ø)
ScoutSuite/providers/aws/facade/sns.py	39.28% <39.28%> (ø)
ScoutSuite/providers/aws/configs/services.py	49.18% <50%> (ø)	⬆️
ScoutSuite/providers/aws/facade/facade.py	37.5% <6.66%> (-6.36%)	⬇️
ScoutSuite/providers/aws/resources/sns/service.py	83.33% <83.33%> (ø)
ScoutSuite/output/js.py	25% <0%> (-0.36%)	⬇️
...tSuite/providers/aws/resources/rds/subnetgroups.py	50% <0%> (ø)
... and 10 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 77e95ff...b050bb4. Read the comment docs.

[Aboisier]

Looks good to me!