RUM-501 Handle Android Strict Mode

[xgouchet]

What does this PR do?

This tries to handle some StrictMode warnings happening during the SDK initialization, which can't easily be deferred to background threads.

Motivation

Prevent the SDK from spamming warnings in host application when StrictMode feature is enabled.

[0xnm]

Let's mark it as InternalApi.

[codecov-commenter]

Codecov Report

Merging #1663 (ac07eec) into develop (a340c76) will increase coverage by 0.05%.
Report is 2 commits behind head on develop.
The diff coverage is 93.75%.

❗ Current head ac07eec differs from pull request most recent head edb5195. Consider uploading reports for the commit edb5195 to get more accurate results

@@             Coverage Diff             @@
##           develop    #1663      +/-   ##
===========================================
+ Coverage    83.64%   83.68%   +0.05%     
===========================================
  Files          458      459       +1     
  Lines        15767    15775       +8     
  Branches      2354     2353       -1     
===========================================
+ Hits         13187    13201      +14     
+ Misses        1946     1945       -1     
+ Partials       634      629       -5     

Files	Coverage Δ
...n/kotlin/com/datadog/android/core/StrictModeExt.kt	100.00% <100.00%> (ø)
...n/com/datadog/android/core/internal/CoreFeature.kt	87.79% <100.00%> (+0.05%)	⬆️
...dog/android/ndk/internal/NdkCrashReportsFeature.kt	68.63% <100.00%> (+1.96%)	⬆️
...rc/main/java/com/datadog/opentracing/DDTracer.java	57.02% <75.00%> (+0.54%)	⬆️

... and 19 files with indirect coverage changes