Unit-Tests for Campaigns

[ashishkumar468]

Description (required)

Added unit-tests for CampaignsPresenter

What changes did you make and why?

Fetch IO & MainThreadScheduler from AppModule in CampaignsPresenter, add unit-tests for Campaigns Presenter

Tested {betaDebug} on OnePlus-3 with API level {27}.

[tests-checker]

Could you please add tests to make sure this change works as expected?

[codecov-io]

Codecov Report

Merging #3258 into master will increase coverage by 0.23%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #3258      +/-   ##
=========================================
+ Coverage    6.31%   6.54%   +0.23%     
=========================================
  Files         270     270              
  Lines       11610   11613       +3     
  Branches      906     906              
=========================================
+ Hits          733     760      +27     
+ Misses      10823   10793      -30     
- Partials       54      60       +6

Impacted Files	Coverage Δ
...free/nrw/commons/campaigns/CampaignsPresenter.java	52.94% <100%> (+52.94%)	⬆️

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