MLIBZ-2581: replacing all fatalErrors() calls to throw Errors instead

[heyzooi]

Description

Replacing all fatalErrors() calls to throw Errors instead so the user can recover from it

Changes

• Many files affected since once a method is marked as throws, meaning it can throw an Error, all methods that calls the method need to either handle the error or rethrows the error

Tests

• Same unit tests is actually the best way test the change, with a few changes where the unit tests where expecting a fatalError()

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (develop@c35ca13). Click here to learn what that means.
The diff coverage is 79.71%.

@@            Coverage Diff             @@
##             develop     #305   +/-   ##
==========================================
  Coverage           ?   88.82%           
==========================================
  Files              ?       71           
  Lines              ?     8840           
  Branches           ?        0           
==========================================
  Hits               ?     7852           
  Misses             ?      988           
  Partials           ?        0

Flag	Coverage Δ
#Mac	86.96% <78.86%> (?)
#iOS	87.73% <79.65%> (?)

Impacted Files	Coverage Δ
Kinvey/Kinvey/Cache.swift	87.34% <0%> (ø)
Kinvey/Kinvey/PurgeOperation.swift	95.38% <100%> (ø)
Kinvey/Kinvey/SyncManager.swift	100% <100%> (ø)
Kinvey/Kinvey/HttpRequest.swift	80.55% <100%> (ø)
Kinvey/Kinvey/Request.swift	98% <100%> (ø)
Kinvey/Kinvey/GetOperation.swift	100% <100%> (ø)
Kinvey/Kinvey/CountOperation.swift	100% <100%> (ø)
Kinvey/Kinvey/CustomEndpoint.swift	98.42% <100%> (ø)
Kinvey/Kinvey/RemoveByIdOperation.swift	100% <100%> (ø)
Kinvey/Kinvey/User.swift	95.6% <100%> (ø)
... and 18 more

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[thomasconner]

Due to the amount of changes it is hard to determine if anything was missed but from my initial pass everything that was changed made sense and looks good to me. I am approving the PR but we should wait for the tests to complete before merging.