[TESTS][CI] Fixing the timeout problem we have on tests when CI is busy

[rafaelks]

@RocketChat/ios

• Fixed all the timeout issues we had when running tests by changing how Realm works during tests;
• Removed all usage of expectations & dispatches with delays because of Realm;
• Included our Pods in the project repository to avoid downloading it again on CI every time;
• Updated CONTRIBUTING guide to remove all CocoaPods references;
• Reduced total CI time in about 7 minutes (24 minutes to 17 minutes);

Before

After

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop@6156052). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             develop    #2214   +/-   ##
==========================================
  Coverage           ?   29.79%           
==========================================
  Files              ?      383           
  Lines              ?    14435           
  Branches           ?        0           
==========================================
  Hits               ?     4301           
  Misses             ?    10134           
  Partials           ?        0

Impacted Files	Coverage Δ
Pods/FirebaseCore/Firebase/Core/FIRLogger.m	63.04% <ø> (ø)
Pods/FirebaseCore/Firebase/Core/FIRComponentType.m	0% <ø> (ø)
Pods/FirebaseCore/Firebase/Core/FIRDependency.m	0% <ø> (ø)
...baseCore/Firebase/Core/FIRAnalyticsConfiguration.m	0% <ø> (ø)
Pods/FirebaseCore/Firebase/Core/FIRComponent.m	0% <ø> (ø)
Pods/FirebaseCore/Firebase/Core/FIRConfiguration.m	0% <ø> (ø)
Pods/FirebaseCore/Firebase/Core/FIROptions.m	0% <ø> (ø)
...FirebaseCore/Firebase/Core/FIRComponentContainer.m	0% <ø> (ø)
...Core/Firebase/Core/FIRAppAssociationRegistration.m	0% <ø> (ø)
Pods/FirebaseCore/Firebase/Core/FIRBundleUtil.m	0% <ø> (ø)
... and 1 more

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[filipealva]

It's looking great! Thanks for this change @rafaelks, it will help a lot to avoid false positives and keep tests OK 💯