Android SDK 5.8.0

The most important change is the support for Android 12.
Review our documentation for more details.

Bugfixes:

• Fix possible crash in Rich Interstitial (#468)
• Retry on response code 429 (#467)
• Fix rich interstitial customizer to be called (#463)

Feature Additions:

• Android 12 trampoline restrictions (#470)
• Allow public use of PushTracking class (#469)

Other:

• Remove unnecessary code (#473)
• Increase priority for important logs (#472)
• Stop snapshot tests with flag (#471)
• Updating travis (#466)