test: Add BaseUITest class

[philipphofmann]

Add a base class for UITests for the iOSSwift to remove some redundant code.

This PR is based on #3370.

[codecov]

Codecov Report

Merging #3371 (b81c0f3) into revert-3298-fix/disable-apphang-in-the-background (7225fc9) will increase coverage by 0.019%.
The diff coverage is n/a.

@@                                   Coverage Diff                                   @@
##           revert-3298-fix/disable-apphang-in-the-background     #3371       +/-   ##
=======================================================================================
+ Coverage                                             89.257%   89.276%   +0.019%     
=======================================================================================
  Files                                                    500       500               
  Lines                                                  54669     54685       +16     
  Branches                                               19621     19624        +3     
=======================================================================================
+ Hits                                                   48796     48821       +25     
+ Misses                                                  5004      4999        -5     
+ Partials                                                 869       865        -4     

see 14 files with indirect coverage changes

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7225fc9...b81c0f3. Read the comment docs.